Prevalence of overweight or obesity and obesity-related diseases in Qingdao region, China
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《中华医药杂志》英文版
[Abstract] Objective The aim of the present study is to describe the prevalence of overweight or obesity patterns and relevant characters among Qingdao residents aged 25~65 years to reveal the associations between hypertension, diabetes mellitus and dyslipidemia; and try to explore the etiology of epidemic of overweight or obesity worldwide, as well as in the local region. Methods Using the data come from the Qingdao Health and Nutrition Survey 2002, where 7 146 Qingdao residents aged 25~65 years were enrolled, male 2,946 accounting 41.2% and female 4,200 accounting for 58.8%, as subjects to calculate the prevalence of overweight and obesity and to detect the prevalence variations between urban and rural area. The comparisons between urban and rural prevalence were performed using chi-square test.BMI 24 and 28 was defined as cut-off point for overweight and obesity respectively according to the recommendation of the Working Group on Obesity in China 2001. SPSS software has been used to extract the case number of hypertension, diabetes and dyslipidemia in another medical examination database between overweight or obesity and normal body weight stratified by age and gender, regarding the overweight and obesity as explanatory variable, the abnormal conditions as outcomes variable, meanwhile the simple logistic regression was applied to achieve the OR and the 95%CI. Results The prevalence of overweight and obesity were 39.6% and 18.8% respectively among Qingdao adults, it was dramatically higher than the average level of China, the Chinese adults prevalence of overweight and obesity were 22.8% and 7.1% respectively, while in big city were 30.0% and 12.3% respectively, which were claimed in the report of China Health and Nutrition Survey 2002. The prevalence of overweight and obesity increased with the age group in both gender, the prevalence of overweight for male in urban area was 44.5% compared with 35.4% in rural,P<0.01, the increment was enlarged especially for the older. There as no significant difference between urban area and rural in female. The prevalence of obesity for male in urban areas was significantly higher than that in rural area, 20.1% versus 12.0%, P<0.00, for female only in the older age group. The simple logistic regression results illustrated that the overweight and obesity were more likely to be associated with the hypertension, diabetes mellitus and dyslipidemia compared with the normal body weight population, by the range of different diseases the ORs were 2.35, 3.09 and 2.04 for overweight males; 4.31, 3.05 and 2.04 for obesity males; 2.07, 2.31 and 2.01 for overweight females; 4.39, 2.23 and 2.30 for obesity females. Conclusions The results of the study indicated that the emergence of overweight and obesity epidemic is an alarming public health problem in Qingdao region. The prevalence of overweight and obesity were attributed to nutrition transition and lifestyle; it is closely associated with certain cardiovascular disease risk factors including hypertension, diabetes mellitus and dyslipidemia. Currently, in order to decrease the incidence of cardiovascular diseases, the effective strategies and programs for controlling the risk factors should be generated in the community level. Furthermore, measures for preventing excess nutrient intake and promoting physical activity should be carried out by Qingdao public health agencies.
[Key words] overweight;obesity;prevalence;BMI;Qingdao,China
INTRODUCTION The nutrition and health status of people is an important indicator for the economy and social development, health care level and the population diathesis of a country or region. Good nutrition and health status not only forms the foundation for the social and economic development, but is also the goal of the country's social and economic development. Many countries in the world particular in the advanced countries, have been conducting regular surveys on the status of nutrition and health among the people, with survey results being released in time, and based on the survey results, relevant social development policies have been formulated
1.The Fifth People's Hospital of Qingdao,Qingdao 266002,Shandong Province,China
2.School of Public Health,Medical and Health Science Center,Universtity of Debrecen,Debrecen,Hungary
Correspondence to TIAN Tao,the Fifth People's of Qingdao 266002,Shandong Province,China
Tel:+86-532-85739208,(0)13156886177 E-mail:tiantao@public.qd.sd.cn
and evaluated accordingly in a view to improve the status of nutrition and health among the people and to promote the coordinated development of social economy.
Obesity is a complex condition, one with serious social and psychological dimensions, that affects virtually all age and socioeconomic groups and threatens to overwhelm both developed and developing countries. In 1995, there were an estimated 200 million obeseadults worldwide and another 18 million under-five children classified as overweight. As of 2000, the number of obese adults has increased to over 300 million[1]. Generally, obesity is diet-related diseases accompany with hypertension, high serum cholesterol, insulin resistance, and other metabolic disturbances that are strong risk factors for other chronic diseases, especially coronary heart disease[2].These diseases are quickly becoming the leading causes of death in many developing countries[3]. In the period of 1989~2000,an increasing prevalence of overweight among Chinese adult was from 17.7% to 28.5%[4].In China from 1960 through 1962, cancer, cerebrovascular disease, and heart disease were the sixth, seventh, and eighth most common causes of mortality in Shanghai, but from 1978 through 1980 they had become the three leading causes of death in that area[5]. Now the obesity present a huge public health threat should be stressed and investigated. It is essential to highlight the associations between the risk factors and explore the etiology of this certain no communicable disease.
As we known the cross-sectional study is one kind of descriptive epidemiological study, meanwhile it is also called “ prevalence” study[6]. I will describe some overweight and obesity patterns among Qingdao adults aged 25~65 by comparing the case number of hypertension, dyslipidemia and diabetes mellitus between overweight or obese and normal body weight po pulations in order to formulate the hypothesis that there are some associations between overweight or obesity and the above conditions and to explore the etiology of the epidemic of overweight or obesity by investigating environment determinants, especially dietary nutrition.
SUBJECTS AND METHODS
Background
The study subjects were draw from the results of Qingdao Health and Nutrition Survey that was conducted in October, 2002.This survey is a part of the China Health and Nutrition Survey, which was the first comprehensive health and nutrition survey in China, under the joint leadership of the Ministry of Health, the Ministry of Science and Technology and the National Bureau of Statistic, it has systematically organized several previously separate surveys on nutrition, hypertension, diabetes, etc. into one survey, and increased some new relevant indicators to be taken into account of the status of social economic development. This survey covered 31 provinces and autonomous region of China. Qingdao is a representative of eastern coastal and relatively developed region in China, it is located in the south of Shandong Peninsula, between the 119.30' and 121.00' east longitude, 35.35' to 37.09' north latitude, with the Yellow Sea to its east and south (Map 1).The total area of the region is 10 654 square kilometers. The downtown area (consisting of 7 districts, named City South, City North, Sifang, Licang, Laoshan,Chengyang, and Huangdao),the rural area comprised by 5 cities of Jiaozhou, Jimo, Pingdu, Jiaonan, and Laixi. The population is approximately 7 million and the GDP reached RMB 178 billion in 2003.
Map 1 Shandong Province
Survey Design
A multi-stage, random cluster sampling procedure was used to draw the sample from each of the region.Qingdao region were stratified by urban and rural area. The sample size estimates by the prevalence of diabetes among adult aged over 20 as documented in the 2001 Qingdao Diabetes Survey. The figure is 5.8%, therefore the total minimum sample size is 12 480, and considering the proportion of over 20 populations is 75% and the rate of unsuccessful interview is 10%, the reasonable survey sample size should be 18 489 (12 480/0.75×0.90). The villages and districts were taken as basic units of study selected by random approach, the locations where the samples were draw out are representative for Qingdao region. This survey included four parts, the questionnaire survey that conducted mainly by using tabulates, health examination, laboratory tests, and dietary survey. The key anthropometrical measurements were obtained from all survey participants. Trained health care workers who followed standard protocol and techniques carried out these measurements. Weight was measured in light indoor clothing without shoes to the nearest tenth of a centimeter with a portable stadimeter. Each of these measurements was completed by at least two health care workers; one worker took the measurements, and another recorded the readings. Special training in anthropometrical measurement techniques was provided at the beginning of the survey. Every subject's blood pressure values were measured twice following the instructions of the survey handbook.Using the disposal syringe needles obtain the fasting blood sample in the morning without breakfast and separated or stored in blood specimen vacuum tubes, the quality control serum was used for blood lipid measurement was provide by the British Randox company. The AU-400 Mold Olympus auto-biochemistry analysis device was used the blood glucose and hemoglobin measurement, adopted national quality control serum. In order to ensure the accuracy of the survey data, a whole process quality control was performed throughout the survey, and all quality control results indicated that every part of the survey met the requirements of the quality control plans in the program design[7].
Data Definition
The both overweight and obesity in this study were defined as the body mass index (BMI,weight in kilograms/ height in meters squared, unit kg/m2)> 24 and > 28 as cut-off point, especially according to the recommendation of the Working Group on Obesity in China 2001. Why these cut-off points were applied will be discussed in details later. The hypertension diagnostic criteria followed the WHO guidelines as the systolic blood pressure≥140mmHg and diastolic blood pressure≥90mmHg; the blood lipid concentration thresholds refer to China National Blood Lipid standards, TC≥5.72mmol/L, TG≥1.70 mmol/L, LDL-C ≥3.64mmol/L, HDL-C<0.91 mmol/L. Each element of this lipid panel above the baseline we defined as dislipidemia. Glucose oxidize enzyme method was used in the fasting plasma glucose test, with the normal range of 3.9~6.1 mmol/L[7].
Statistical Analysis
Using the survey database we identified subjects aged 25~65 by gender and areas, calculated the BMI (weight in kilograms/ height in meters squared, unit kg/m2) for the anthropometrical measurement results, BMI was defined 24 ≤ BMI ≤28 as overweight, BMI > 28 as obesity, 18≤ BMI < 24 as normal. The prevalence of overweight and obesity was caculated in each age group specified by gender and area, and the comparisons between urban and rural prevalence were performed using chi-square test. The case number of hypertension, diabetes and dislipidemia was obtained for another medical examination database, save individual categorized in overweight or obesity and normal body weight group stratified by age and gender. Regarding the overweight and obesity as the risk factors, the abnormal conditions as outcomes, the simple logistic regression was applied to achieve the OR and the 95% CI. All statistical analysis were undertaken using SPSS version 11.0 (SPSS for Windows, Chicago: 2002) and Epi Info 6.0.
RESULTS
There were 7,146 residents aged 25~65 years enrolled to the survey, male 2 946,41.2%; female 4 200, 58.8%. The overall impression was the overweight and obesity prevalence increased by age span, regardless variation of gender and areas(Figure 1,Figure 2).The prevalence of overweight and obesity was 39.6% and 18.8% respectively in Qingdao adults. In all age groups for male (Figure 1),the overweight prevalence in urban area was higher than that in rural area, especially for older age group,the total prevalence in city was significantly higher than that in the countryside,(44.5% vs 35.4%,P<0.01).In the relative younger age group of 25~, 35~ for male,there is no significant difference,(33.8% vs 28.6%, P>0.05; 42.1% vs 37.7%,P>0.05 respectively), in relative older age group of 45~ and 55~65 years, the prevalence in urban area was higher than that in rural area(42.8% vs 36.2%, P=0.05; 50.2% vs 36.5%, P<0.00,respectively).For female the result was very interesting (Figure 2), the overall overweight prevalence in the urban area and rural was almost equal, 39.4% to 40.6%, in the younger age group 25~, 35~, the prevalence in rural area was inversely higher than that in urban area(33.8% vs 24.7%,P<0.02; 41.9% vs 33.9%,P<0.02,respectively), it was an another story that in the relatively older age group of 45~ and 55~65 years,where the prevalence in two area was almost equal (41.8% vs 42.5% and 43.3% vs 43.9%).
Figure 1 The prevalence of over weight in male in urban and rural area,Qingdao 2002
Figure 2 The prevalence of over weight in female in urban and rural area,Qingdao 2002
The tendencies of the prevalence of obesity increased with age, except for males in the rural area (Figure 3,Figrure 4).The total prevalence of obesity for male in urban was significantly higher than that in rural area, 20.1% vs 12.0%,P<0.00 (Figure 3); by different age group, for male in 25~, 35~, there were no significant variations by area(15.5% vs 15.1%,P>0.05;14.7% vs 11.5%, P>0.05); in the older age group of 45~ and 55~65, the prevalence of obesity in urban area was dramatically higher than rural area(22.0% vs 11.2%,P<0.00; 22.4% vs 11.4%,P<0.00), the obesity prevalence in urban area was almost two times higher than that in rural area. For female general prevalence of obesity was 23.1% in urban, 20.5% in rural,P=0.05(Figure 4).In younger age group of 25~, 35~, there were no significant differences between urban and rural populations (11.8% vs 8.8%,P>0.05; 18.5% vs 18.3% P>0.05, respectively).In the group of 45~, the prevalence in rural area was higher than that in cities(26.7% vs 21.0%,P<0.05); in group 55~65, the urban prevalence was higher than the rural one,(30.7% vs 24.2%,P<0.05).
Figure 3 The prevalence of obesity in male in urban and rural area,Qingdao 2002
Figure 4 The prevalence of obesity in female in urban rural area,Qingdao 2002
The case number of hypertension HBP, diabetes mallitus(DM) and dyslipidemia were categorized by overweight, obesity and normal body weight specified by gender. We could find that there was a large number of cases in the overweight or obese population compared with the normal body weight group (Table 1).
Table 1 The number of cases of HBP, DM and dyslipidemia in various body weight categaries aged 25~65 years
Note:0 indicating non- disease, 1 indicating diseases
Since in younger age group less people undenwent the blood test, the age-stratified data was invalid for logistic regression analysis. In this study overweight, obesity and normal body weight were taken as explanatory variables, the diseases hypertension, diabetes and dyslipidemia were taken as outcome variables, and simple logistic regression was applied to obtain the odds ratio(OR). The results (Table 2) indicated that both overweight and obese individuals were more likely to suffer from hypertension, diabetes and dyslipidemia comparing with people of normal body weight for both gender, in another words,they had higher risk for being ill than the normal. The times of risk for overweight in male by difference disease were 2.35, 3.09 and 1.46; for obesity male,were 4.31, 3.05 and 2.04; for overweight females were 2.07,2.31 and 2.01; for obesity females were 4.39, 2.23 and 2.30. It was obviously that the obesity had the highest risk for suffering these certain diseases.
Tab 2 The association between overweight or obesity and HBP, DM and dyslipidemia
DISCUSSION
The prevalence of overweight and obesity were 39.6% and 18.8% respectively among Qingdao adults, it was dramatically higher than the Chinese average level of 22.8% and 7.1%. The prevalence of overweight and obesity increased with age in both gender. The prevalence of overweight for males in the urban area was 44.5% compared with 35.4% in the rural area,P<0.01, the increment was enlarged especially for the older. There was a little difference between urban and rural population in females. The prevalence of obesity for male in urban area was significant higher than that in rural area(20.1% versus 12.0%,P<0.00), for females significant difference was observed only in the older age group. The simple logistic regression results illustrated that the overweight population had two times higher risk for suffering hypertension than the normal body weight people among both gender, for obesity was more than four times higher. In both overweight and obese populations there was were more than three times higher risk to be ill with diabetes in male and more than two times in female comparing with the normal body weight; shifting to dyslipidemia, for male overweight has one and half times higher risk than the normal, the obesity was more than two times higher risk for developing dyslipidemia, for female both obesity and overweight the risk were more than two times higher.
Before unfolding our discussion, the most important thing is to answer the following crucial questions. How to define the cut-off point of overweight and obesity? Why WHO define the BMI 25 and 30 as the cut- off point for overweight and obesity? Are the criteria suitable for various races all over the world? Why China adopted the BMI 24 and 28 as their overweight and obesity cut-off point in this national comprehensive health and nutrition survey and how to define it.
The WHO has issued universal BMI standards for defining overweight and obesity in adults BMI≥25,and ≥30 respectively based on the risk of obesity-related disease in Europeans. Although widely used, there is mounting evidence suggesting that these standards are not appropriate for all populations. The need for a lower MBI to classify overweight and obesity in Asian population has been controversial. Research indicates that the associations between BMI and health risk can vary between different ethnicities[8].For prevention of obesity in the Chinese population, it is necessary to define the optimal range of healthy weight and the appropriate cut-off points of body mass index (BMI) and waist circumference for Chinese adults. The Working Group on Obesity in China under the support of the International Life Sciences Institute Focal Point in China organized a meta-analysis on the relationship between BMI, waist circumference and risk factors of related chronic diseases (e.g., high diabetes, diabetes mellitus, and lipoprotein disorders). In thirteen population studies all met the criteria for enrollment, with data of 239 972 adults (20~70 years of age) surveyed in the 1990s. Data on waist circumference was available for 111, 411 persons, and data on serum lipids and glucose were available for more than 80, 000. The prevalence of hypertension, diabetes, dyslipidemia and clustering of risk factors all increased with increasing levels of BMI or waist circumference. A BMI of 24 with best sensitivity and specificity for identification of the risk factors was recommended as the cut-off point for overweight; a BMI of 28, which may identify the risk factors with specificity around 90%, was recommended as the cut-off point for obesity. Analysis of a population-attributable risk percentage illustrated that reducing the BMI to the normal range (<24) could prevent 45%~50% of the clustering of risk factors. Treatment of obese persons (BMI = 28) with drugs could prevent 15%~17% of clustering of risk factors. Based on these guidelines, a classification of overweight and obesity for Chinese adults is recommended[9]. Based on above BMI cut-offs for Chinese adults, the overweight and obesity prevalence in China 2000 were 33.6% and 7.6%, respectively, however, if WHO criteria were applied, overweight and obesity prevalence of Chinese adults would be 24.5% and 3.0% respectively, but it can not reflect the potential risk factors completely[10].
This opinion is also consensus with population strategy of prevention theoretically; attempt to control the determinants of prevalence, to lower the mean level of risk factors, to shift the whole distribution of exposure in a favorable direction, to maximize the positive implications in public health fields[11]. Before the new overweight and obesity cut-off point generated specific for Chinese in 2001,most of the research study related overweight or obesity applied the WHO cut-off points. Since different cut-off points were accepted between this study results and other West Country research studies, there was no condition to compare with each other, but it is essential to note the world trends of obesity was not optimistic, and some countries presented with special characters and were benefit to cooperate to fight the epidemic of the overweight and obesity all over the world. According to World Health Organization (WHO) statistics the prevalence of obesity in European countries increased to 10%~20% during the past years and it is even higher than that in the countries of Eastern Europe[12]. During the period of 1980~1991 the prevalence of obesity in the United States reached 30%[13].The First Hungarian Representative Nutrition Study (16 641 participants) carried out in 1985~1988 by the National Institute of Food Hygiene and Nutrition (NIFHN) [14]showed that 62% for women and 58% for men were overweight or obesity in 1985. The 1992~1994 Nutrition Survey conducted by the NIFHN (2 559 participants) [15] measured 49% and 63% overweight or obesity for women and men. The Heart Healthy Nutrition in Hungary Project subsidized by the World Bank PMU of the Ministry of Welfare carried out as a repeated questionnaire-based survey of nutritional habits beginning in spring 1997 (the same 3 000 respondents interviewed on several occasions) estimated the prevalence of obesity and overweight was 39% for the population[16]. Obviously, the situation in Hungary was optimistic with the declined prevalence of obesity and overweight. But in the report of National Health Interview Survey 2003, 29% of female and 38% of male are overweight, whereas 1 out of 5 adults qualifies as obese, the prevalence of obesity among men aged 65 and over has almost doubled to 30% from its 2000 value of 17%[17].
As a result, the findings in this study are similar with the study of Dr Wang Huijun, and Zhai Fengying, they also applied the new definition of BMI 24 and 28 as the cut-off point for overweight and obesity. They used the data from 1989,1991,1993,1997 and 2000 Chinese Nutrition and Health Survey, the longitudinal survey was conducted by the cooperation with the Carolina Population Center at the University of North Carolina, the National Institute of Nutrition and Food Safety, and the Chinese Center for Disease Control and Prevention coordinated by Pro. Popkin.The subjects were aged 18~45 adults, revealed that the overweight prevalence of both male and female elevated dramatically in the period of 1989~2000, for male from 11.9% to 27.9%, increase 16% in this eleven years, for female from 17.7% to 28.5%, increased 10.8%.The magnitude of overweight in male is wider than that in female, the relative older age groups were higher than younger groups, the prevalence was difference by variation of area, for male in urban area the overweight prevalence was apparently higher than that in rural place, for female in young age group the prevalence in urban is lower than that in rural place, in older age group the profile was contrary[4].
Until now the overall impression of the overweight or obesity is in our mind, I try to clarify the real causation of the epidemic worldwide particular for Qingdao region. Focusing on etiologic factors, the National Institute of Health,USA claimed that obesity is a complex multifactorial chronic disease that develops from an interaction of genotype and the environment[18].Highlighting the environment determinants in my opinion that excess fat intake and commuting physical activity played an important role in the etiology of the obesity epidemic. The daily consumption of animal products for the urban and rural residents has increased from 210 grams and 69 grams respectively in 1992 to 248 grams and 126 grams in 2002, the daily consumption of oils among urban residents increased to 44 grams from 37 grams in 1992. According to the 1982,1992 and 2002 nutrition survey reports, the China average fat intake per day increased from 48.1 g in 1982 to 58.3 g in 1992, then to 76.2 g in 2002 (Table 3). In Qingdao region the figure reached to 90.8 g in 2002 survey, this probably is a good explanation for why Qingdao has a higher prevalence on obesity compare with national average level. In this study the overweight and obesity prevalence of Qingdao people are 39.6% and 18.8% respectively, in the report of China Health and Nutrition Survey 2002, the Chinese adults prevalence of overweight and obesity was 22.8% and 7.1% respectively, while in big city the figure were 30.0% and 12.3% respectively, which was dramatically higher than the overall national level.
Even though there were different of opinions about whether the percentage of dietary fat plays an important role in the rising prevalence of overweight and obesity. We believe that ample research from animal and clinical studies, from controlled trials, and from epidemiological and ecological analyses provided strong evidence that dietary fat plays a role in the development and treatment of obesity. A reduction in fat intake reduces the gap between total energy intake and total energy expenditure and thus an effective strategy for reducing the present epidemic of obesity worldwide. In Pro.Popkin' s study showed that reduction of 10% in the proportion of energy from fat was associated with a reduction in weight of 16 g/d[19].
Table 3 1982,1992 and 2002 national average nutrients intake by urban & rural population in China (reference person/day)
Note:A reference person = 18 years old man who performs physical activity
Data from Ministry of Health,China
Changes in dietary composition, which correspond to socioeconomic growth, may accelerate the prevalence of obesity in China. The composition of the Chinese diet has been shifting towards a larger quantity of animal products, a higher fat intake, and lowers in carbohydrates and fiber[20]. Diet is becoming an increasingly important determinant of body weight in China population, where fat and energy consumption has been increasing steadily during the past decade. Change in fat intake was positively associated with change in BMI in men, and change in physical activity level was inversely associated with change in BMI in women. Energy intake, physical activity and major socio-economic factors were related to BMI in cross-sectional analysis[21]. For males, energy intake below 95% of the Chinese RDA was associated with significantly smaller gains in circumference (WC) and greater loss of mid arm muscle area (MAMA) than energy intake between 95%~125% RDA. For both sexes, protein intake below 10.4% of energy was associated with significantly greater loss of MAMA than intake between 10.4%~12.1% of energy. For females, energy intake above 125% RDA was associated with significantly greater gains in body fat than intake between 95%~125%[22]. According to the findings of Qingdao survey 2002, residents energy intake contribution from fat had reached 35.3 %, exceeding the upper limit of 30 % recommended by the World Health Organization. The situation was more serious in the urban area, this maybe the reasonable explanation of why the prevalence of overweight or obesity is high dramatically in the urban population. In another study of Pro.Popkin present a similar result, among the Chinese adults, dietary energy and fat intakes were positively and significantly associated with the BMI. Household income and physical activity level were also significantly associated with BMI in urban residence and higher incomes were associated with lower energy intake, higher fat intake, and lower physical activity level compared to rural residents and other income categories[23]. Additionally, decreased level of physical activity and leisure are linked to increases in the prevalence of an overweight condition, obesity and diet-related non-communicable diseases [24] In summary, numerous reliable research study convinced that the dietary nutrition transition in terms of more over fat consumption as well as commuting physical activity are strongly associated with the overweight or obesity epidemic.
In this study took the overweight and obesity as the explanatory variables, certain unhealthy conditions as outcome variables, the results indicated that the overweight and obesity were more likely become unhealthy status. If we altered the perspective, taking the unhealthy conditions as explanatory variable, overweight and obesity as outcome variables, again the individuals with unhealthy conditions were more likely gain excess adipose. Those kinds of relationships were illustrated by tremendous studies in different countries. Obesity was significantly associated with a history of diabetes mellitus (18% vs 7%,P<0.05) and hypertension (48% vs 28%,P<0.05). Compared to the non-obese, those who were obese had a higher level of serum uric acid [(311 ± 102)mol/L vs (280 ± 96) mol/L,P<0.05 ]and triglyceride [(2.67± 1.95)mol/L vs (1.86 ± 0.95) mmol/L,P<0.05]. The high prevalence of obesity both in elderly men and women and its strong association with chronic diseases causes economical and social burden for Hungary[25].The results in this study are very close to the Korean statement, in the 1998 Korea Health and Nutrition Examination Survey, which reported that the prevalence of diabetes, hypertension, and dyslipidemia has doubled at a BMI of 23.0 to 24.0 and tripled at a BMI of 26.0 in the Korean adult population. The authors propose that body fat distribution at a BMI of 23.0 in Asians may be similar to those in whites at a BMI of 25.0[26].In another study focusing to older Japanese Americans, multiple regression analysis was performed, controlling for factors known to influence blood pressure values, including age, physical activity index, alcohol intake, current smoking status, and diabetes mellitus. The association between BMI and both systolic and diastolic pressures remained highly statistically significant in these analyses. These results show that obesity and high blood pressure continue to be highly correlated even in old age and suggest that it may be possible to modify incidence of hypertension by changes in body weight[27].A follow up study from 12 Chinese Provinces showed that the prevalence of diabetes in both males and females with BMI>24 and >28 were 23.2% and 18.5% respectively compared with normal body weight were 4.08% and 3.66%[6].Apparently, those series of clinic manifestations developed simultaneously and promoted each other, and presented the common profiles related to metabolic disorders influenced by endocrine system. Obesity is the tip of the iceberg of a cluster of cardiovascular disease risk factors, including hypertension, diabetes, and dyslipidemia, otherwise known as the “Metabolic Syndrome”, “New World Syndrome”, or “Deadly Quartet”. This natural consequence will be an epidemic of cardiovascular complications, such as coronary heart disease and stroke as well as microvascular complications. In the famous Framingham study, 5,209 subjects for both gender were followed for 26 years, using multiple logistic regression to analysis, the obesity was the independent risk factor for cardiovascular disease in both gender[28].Obesity, hyperinsulinaemia, and insulin resistance are characteristic features of Hong Kong Chinese patients who have various component of the metabolic syndrome. There was an increased risk of 3.1 and 5 times when the body BMI was 23.0~24.9 and ≥25, respectively[29].Another crucial evidence also strongly supports the theory that the Metabolic Syndrome is recognized as a high risk factor to CVD. According to WHO MONICA China section report the coronary heart disease incidence increased by 67% between 1984~1997 in male, the average increase was 2.1% annually (P<0.05). We should pay more attention to the report findings,as the incidence of coronary heart disease in Qingdao region was the highest for males figured 108.7/100 000 compared with the lowest one in Anhui Tuzhou region figured 3.3/100 000, the variation between two region was 32.9 times[30].Again the only reasonable explanation is that the risk factors of obesity epidemic in Qingdao region are significantly higher than that in other regions. Let us see the issue from the opposite perspective, if we had controlled the risk factors of Metabolic Syndrome successfully, whether the incidence of CHD will be declined or not. The North Karelia project pilot for Finland from 1972 to 1997 presented the positive answer, as a result of preventive activity, the total mortality decreased by 49%, CVD mortality decreased by 68%, CHD mortality decreased by 73%, in the 35~64 age group in both gender. Therefore this study provides the scientific evidence supports the point that the fatty dietary habits extensively contribute to the Metabolic Syndrome by environmental aspect.
The limitation of this study is that there are some confounders such as the age, socioeconomic status, location, alcohol consumption and level of physical activity, which can distort the associations between the exposure and the outcome. The multiple logistic regression molds should be formulated in a way to control the confounders in the future research study. Further investigations using analytical epidemiological methodology should be carried out to examine the hypothesis whether the over nutrition diet lead to overweight or obesity in diverse populations and areas. The accurate measurement of diet composition is extremely essential to determine the relations between unbalanced nutrition and obesity.
By conclusion, the present study indicates that overweight and obesity are emerging public health problems with an alarming rate in Qingdao region as well as nationwide in China. If no effective strategies or programs will be established to fight and control the risk factors, including obesity, diabetes, hypertension, dyslipidemia, the obesity-related non communicable diseases will be prevalent in the near future and will elevate the socioeconomic burden dramatically. My personal view is that our municipal public health agency should refer to the experiences in the North Karelia Project for formulating the proposal of Healthy City Programm. Governments at all levels are called to strengthen public education, health promotion activities and advocate a balanced diet and a healthy lifestyle. Surveillance and intervention programs to modify the risk factors should be appropriately implemented by community level, meanwhile we should evaluated our strategies or programs with epidemical analytical approaches and follow the cost-effective principles. To improve the situation, the government should ensure to implement laws and regulations concerning nutrition, such as requiring certification of nutritionists and nutritional content of foods such as policosanol, plant stanols, soy isoflavones, omega-3 fatty acids[31].A national scientific diet intake guideline based on nutrition science evidences should also be established and available, to provide authoritative information so that the public can choose food and do physical exercise scientifically. China will also enhance guidance in agriculture and food production, distribution and marketing to help improving people's nutrition and health.
Acknowledgement
I would like to express my deepest gratitude for Pro. Zengchang Pang the director of Qingdao Center for Disease Control and Prevention for his kindly providing the Survey data and allowing me work in Center temporarily. The Dr. Shaojie Wang and Dr. Xiaorong Chen also raised helpful comments on how to extract the case number from the database. My supervisor Dr.Bardors also delivered me many valuable advices and suggestions on how to use survey data design my study.
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(Editor Jaque )(TIAN Tao1，Bárdos Helga2,A)
[Key words] overweight;obesity;prevalence;BMI;Qingdao,China
INTRODUCTION The nutrition and health status of people is an important indicator for the economy and social development, health care level and the population diathesis of a country or region. Good nutrition and health status not only forms the foundation for the social and economic development, but is also the goal of the country's social and economic development. Many countries in the world particular in the advanced countries, have been conducting regular surveys on the status of nutrition and health among the people, with survey results being released in time, and based on the survey results, relevant social development policies have been formulated
1.The Fifth People's Hospital of Qingdao,Qingdao 266002,Shandong Province,China
2.School of Public Health,Medical and Health Science Center,Universtity of Debrecen,Debrecen,Hungary
Correspondence to TIAN Tao,the Fifth People's of Qingdao 266002,Shandong Province,China
Tel:+86-532-85739208,(0)13156886177 E-mail:tiantao@public.qd.sd.cn
and evaluated accordingly in a view to improve the status of nutrition and health among the people and to promote the coordinated development of social economy.
Obesity is a complex condition, one with serious social and psychological dimensions, that affects virtually all age and socioeconomic groups and threatens to overwhelm both developed and developing countries. In 1995, there were an estimated 200 million obeseadults worldwide and another 18 million under-five children classified as overweight. As of 2000, the number of obese adults has increased to over 300 million[1]. Generally, obesity is diet-related diseases accompany with hypertension, high serum cholesterol, insulin resistance, and other metabolic disturbances that are strong risk factors for other chronic diseases, especially coronary heart disease[2].These diseases are quickly becoming the leading causes of death in many developing countries[3]. In the period of 1989~2000,an increasing prevalence of overweight among Chinese adult was from 17.7% to 28.5%[4].In China from 1960 through 1962, cancer, cerebrovascular disease, and heart disease were the sixth, seventh, and eighth most common causes of mortality in Shanghai, but from 1978 through 1980 they had become the three leading causes of death in that area[5]. Now the obesity present a huge public health threat should be stressed and investigated. It is essential to highlight the associations between the risk factors and explore the etiology of this certain no communicable disease.
As we known the cross-sectional study is one kind of descriptive epidemiological study, meanwhile it is also called “ prevalence” study[6]. I will describe some overweight and obesity patterns among Qingdao adults aged 25~65 by comparing the case number of hypertension, dyslipidemia and diabetes mellitus between overweight or obese and normal body weight po pulations in order to formulate the hypothesis that there are some associations between overweight or obesity and the above conditions and to explore the etiology of the epidemic of overweight or obesity by investigating environment determinants, especially dietary nutrition.
SUBJECTS AND METHODS
Background
The study subjects were draw from the results of Qingdao Health and Nutrition Survey that was conducted in October, 2002.This survey is a part of the China Health and Nutrition Survey, which was the first comprehensive health and nutrition survey in China, under the joint leadership of the Ministry of Health, the Ministry of Science and Technology and the National Bureau of Statistic, it has systematically organized several previously separate surveys on nutrition, hypertension, diabetes, etc. into one survey, and increased some new relevant indicators to be taken into account of the status of social economic development. This survey covered 31 provinces and autonomous region of China. Qingdao is a representative of eastern coastal and relatively developed region in China, it is located in the south of Shandong Peninsula, between the 119.30' and 121.00' east longitude, 35.35' to 37.09' north latitude, with the Yellow Sea to its east and south (Map 1).The total area of the region is 10 654 square kilometers. The downtown area (consisting of 7 districts, named City South, City North, Sifang, Licang, Laoshan,Chengyang, and Huangdao),the rural area comprised by 5 cities of Jiaozhou, Jimo, Pingdu, Jiaonan, and Laixi. The population is approximately 7 million and the GDP reached RMB 178 billion in 2003.
Map 1 Shandong Province
Survey Design
A multi-stage, random cluster sampling procedure was used to draw the sample from each of the region.Qingdao region were stratified by urban and rural area. The sample size estimates by the prevalence of diabetes among adult aged over 20 as documented in the 2001 Qingdao Diabetes Survey. The figure is 5.8%, therefore the total minimum sample size is 12 480, and considering the proportion of over 20 populations is 75% and the rate of unsuccessful interview is 10%, the reasonable survey sample size should be 18 489 (12 480/0.75×0.90). The villages and districts were taken as basic units of study selected by random approach, the locations where the samples were draw out are representative for Qingdao region. This survey included four parts, the questionnaire survey that conducted mainly by using tabulates, health examination, laboratory tests, and dietary survey. The key anthropometrical measurements were obtained from all survey participants. Trained health care workers who followed standard protocol and techniques carried out these measurements. Weight was measured in light indoor clothing without shoes to the nearest tenth of a centimeter with a portable stadimeter. Each of these measurements was completed by at least two health care workers; one worker took the measurements, and another recorded the readings. Special training in anthropometrical measurement techniques was provided at the beginning of the survey. Every subject's blood pressure values were measured twice following the instructions of the survey handbook.Using the disposal syringe needles obtain the fasting blood sample in the morning without breakfast and separated or stored in blood specimen vacuum tubes, the quality control serum was used for blood lipid measurement was provide by the British Randox company. The AU-400 Mold Olympus auto-biochemistry analysis device was used the blood glucose and hemoglobin measurement, adopted national quality control serum. In order to ensure the accuracy of the survey data, a whole process quality control was performed throughout the survey, and all quality control results indicated that every part of the survey met the requirements of the quality control plans in the program design[7].
Data Definition
The both overweight and obesity in this study were defined as the body mass index (BMI,weight in kilograms/ height in meters squared, unit kg/m2)> 24 and > 28 as cut-off point, especially according to the recommendation of the Working Group on Obesity in China 2001. Why these cut-off points were applied will be discussed in details later. The hypertension diagnostic criteria followed the WHO guidelines as the systolic blood pressure≥140mmHg and diastolic blood pressure≥90mmHg; the blood lipid concentration thresholds refer to China National Blood Lipid standards, TC≥5.72mmol/L, TG≥1.70 mmol/L, LDL-C ≥3.64mmol/L, HDL-C<0.91 mmol/L. Each element of this lipid panel above the baseline we defined as dislipidemia. Glucose oxidize enzyme method was used in the fasting plasma glucose test, with the normal range of 3.9~6.1 mmol/L[7].
Statistical Analysis
Using the survey database we identified subjects aged 25~65 by gender and areas, calculated the BMI (weight in kilograms/ height in meters squared, unit kg/m2) for the anthropometrical measurement results, BMI was defined 24 ≤ BMI ≤28 as overweight, BMI > 28 as obesity, 18≤ BMI < 24 as normal. The prevalence of overweight and obesity was caculated in each age group specified by gender and area, and the comparisons between urban and rural prevalence were performed using chi-square test. The case number of hypertension, diabetes and dislipidemia was obtained for another medical examination database, save individual categorized in overweight or obesity and normal body weight group stratified by age and gender. Regarding the overweight and obesity as the risk factors, the abnormal conditions as outcomes, the simple logistic regression was applied to achieve the OR and the 95% CI. All statistical analysis were undertaken using SPSS version 11.0 (SPSS for Windows, Chicago: 2002) and Epi Info 6.0.
RESULTS
There were 7,146 residents aged 25~65 years enrolled to the survey, male 2 946,41.2%; female 4 200, 58.8%. The overall impression was the overweight and obesity prevalence increased by age span, regardless variation of gender and areas(Figure 1,Figure 2).The prevalence of overweight and obesity was 39.6% and 18.8% respectively in Qingdao adults. In all age groups for male (Figure 1),the overweight prevalence in urban area was higher than that in rural area, especially for older age group,the total prevalence in city was significantly higher than that in the countryside,(44.5% vs 35.4%,P<0.01).In the relative younger age group of 25~, 35~ for male,there is no significant difference,(33.8% vs 28.6%, P>0.05; 42.1% vs 37.7%,P>0.05 respectively), in relative older age group of 45~ and 55~65 years, the prevalence in urban area was higher than that in rural area(42.8% vs 36.2%, P=0.05; 50.2% vs 36.5%, P<0.00,respectively).For female the result was very interesting (Figure 2), the overall overweight prevalence in the urban area and rural was almost equal, 39.4% to 40.6%, in the younger age group 25~, 35~, the prevalence in rural area was inversely higher than that in urban area(33.8% vs 24.7%,P<0.02; 41.9% vs 33.9%,P<0.02,respectively), it was an another story that in the relatively older age group of 45~ and 55~65 years,where the prevalence in two area was almost equal (41.8% vs 42.5% and 43.3% vs 43.9%).
Figure 1 The prevalence of over weight in male in urban and rural area,Qingdao 2002
Figure 2 The prevalence of over weight in female in urban and rural area,Qingdao 2002
The tendencies of the prevalence of obesity increased with age, except for males in the rural area (Figure 3,Figrure 4).The total prevalence of obesity for male in urban was significantly higher than that in rural area, 20.1% vs 12.0%,P<0.00 (Figure 3); by different age group, for male in 25~, 35~, there were no significant variations by area(15.5% vs 15.1%,P>0.05;14.7% vs 11.5%, P>0.05); in the older age group of 45~ and 55~65, the prevalence of obesity in urban area was dramatically higher than rural area(22.0% vs 11.2%,P<0.00; 22.4% vs 11.4%,P<0.00), the obesity prevalence in urban area was almost two times higher than that in rural area. For female general prevalence of obesity was 23.1% in urban, 20.5% in rural,P=0.05(Figure 4).In younger age group of 25~, 35~, there were no significant differences between urban and rural populations (11.8% vs 8.8%,P>0.05; 18.5% vs 18.3% P>0.05, respectively).In the group of 45~, the prevalence in rural area was higher than that in cities(26.7% vs 21.0%,P<0.05); in group 55~65, the urban prevalence was higher than the rural one,(30.7% vs 24.2%,P<0.05).
Figure 3 The prevalence of obesity in male in urban and rural area,Qingdao 2002
Figure 4 The prevalence of obesity in female in urban rural area,Qingdao 2002
The case number of hypertension HBP, diabetes mallitus(DM) and dyslipidemia were categorized by overweight, obesity and normal body weight specified by gender. We could find that there was a large number of cases in the overweight or obese population compared with the normal body weight group (Table 1).
Table 1 The number of cases of HBP, DM and dyslipidemia in various body weight categaries aged 25~65 years
Note:0 indicating non- disease, 1 indicating diseases
Since in younger age group less people undenwent the blood test, the age-stratified data was invalid for logistic regression analysis. In this study overweight, obesity and normal body weight were taken as explanatory variables, the diseases hypertension, diabetes and dyslipidemia were taken as outcome variables, and simple logistic regression was applied to obtain the odds ratio(OR). The results (Table 2) indicated that both overweight and obese individuals were more likely to suffer from hypertension, diabetes and dyslipidemia comparing with people of normal body weight for both gender, in another words,they had higher risk for being ill than the normal. The times of risk for overweight in male by difference disease were 2.35, 3.09 and 1.46; for obesity male,were 4.31, 3.05 and 2.04; for overweight females were 2.07,2.31 and 2.01; for obesity females were 4.39, 2.23 and 2.30. It was obviously that the obesity had the highest risk for suffering these certain diseases.
Tab 2 The association between overweight or obesity and HBP, DM and dyslipidemia
DISCUSSION
The prevalence of overweight and obesity were 39.6% and 18.8% respectively among Qingdao adults, it was dramatically higher than the Chinese average level of 22.8% and 7.1%. The prevalence of overweight and obesity increased with age in both gender. The prevalence of overweight for males in the urban area was 44.5% compared with 35.4% in the rural area,P<0.01, the increment was enlarged especially for the older. There was a little difference between urban and rural population in females. The prevalence of obesity for male in urban area was significant higher than that in rural area(20.1% versus 12.0%,P<0.00), for females significant difference was observed only in the older age group. The simple logistic regression results illustrated that the overweight population had two times higher risk for suffering hypertension than the normal body weight people among both gender, for obesity was more than four times higher. In both overweight and obese populations there was were more than three times higher risk to be ill with diabetes in male and more than two times in female comparing with the normal body weight; shifting to dyslipidemia, for male overweight has one and half times higher risk than the normal, the obesity was more than two times higher risk for developing dyslipidemia, for female both obesity and overweight the risk were more than two times higher.
Before unfolding our discussion, the most important thing is to answer the following crucial questions. How to define the cut-off point of overweight and obesity? Why WHO define the BMI 25 and 30 as the cut- off point for overweight and obesity? Are the criteria suitable for various races all over the world? Why China adopted the BMI 24 and 28 as their overweight and obesity cut-off point in this national comprehensive health and nutrition survey and how to define it.
The WHO has issued universal BMI standards for defining overweight and obesity in adults BMI≥25,and ≥30 respectively based on the risk of obesity-related disease in Europeans. Although widely used, there is mounting evidence suggesting that these standards are not appropriate for all populations. The need for a lower MBI to classify overweight and obesity in Asian population has been controversial. Research indicates that the associations between BMI and health risk can vary between different ethnicities[8].For prevention of obesity in the Chinese population, it is necessary to define the optimal range of healthy weight and the appropriate cut-off points of body mass index (BMI) and waist circumference for Chinese adults. The Working Group on Obesity in China under the support of the International Life Sciences Institute Focal Point in China organized a meta-analysis on the relationship between BMI, waist circumference and risk factors of related chronic diseases (e.g., high diabetes, diabetes mellitus, and lipoprotein disorders). In thirteen population studies all met the criteria for enrollment, with data of 239 972 adults (20~70 years of age) surveyed in the 1990s. Data on waist circumference was available for 111, 411 persons, and data on serum lipids and glucose were available for more than 80, 000. The prevalence of hypertension, diabetes, dyslipidemia and clustering of risk factors all increased with increasing levels of BMI or waist circumference. A BMI of 24 with best sensitivity and specificity for identification of the risk factors was recommended as the cut-off point for overweight; a BMI of 28, which may identify the risk factors with specificity around 90%, was recommended as the cut-off point for obesity. Analysis of a population-attributable risk percentage illustrated that reducing the BMI to the normal range (<24) could prevent 45%~50% of the clustering of risk factors. Treatment of obese persons (BMI = 28) with drugs could prevent 15%~17% of clustering of risk factors. Based on these guidelines, a classification of overweight and obesity for Chinese adults is recommended[9]. Based on above BMI cut-offs for Chinese adults, the overweight and obesity prevalence in China 2000 were 33.6% and 7.6%, respectively, however, if WHO criteria were applied, overweight and obesity prevalence of Chinese adults would be 24.5% and 3.0% respectively, but it can not reflect the potential risk factors completely[10].
This opinion is also consensus with population strategy of prevention theoretically; attempt to control the determinants of prevalence, to lower the mean level of risk factors, to shift the whole distribution of exposure in a favorable direction, to maximize the positive implications in public health fields[11]. Before the new overweight and obesity cut-off point generated specific for Chinese in 2001,most of the research study related overweight or obesity applied the WHO cut-off points. Since different cut-off points were accepted between this study results and other West Country research studies, there was no condition to compare with each other, but it is essential to note the world trends of obesity was not optimistic, and some countries presented with special characters and were benefit to cooperate to fight the epidemic of the overweight and obesity all over the world. According to World Health Organization (WHO) statistics the prevalence of obesity in European countries increased to 10%~20% during the past years and it is even higher than that in the countries of Eastern Europe[12]. During the period of 1980~1991 the prevalence of obesity in the United States reached 30%[13].The First Hungarian Representative Nutrition Study (16 641 participants) carried out in 1985~1988 by the National Institute of Food Hygiene and Nutrition (NIFHN) [14]showed that 62% for women and 58% for men were overweight or obesity in 1985. The 1992~1994 Nutrition Survey conducted by the NIFHN (2 559 participants) [15] measured 49% and 63% overweight or obesity for women and men. The Heart Healthy Nutrition in Hungary Project subsidized by the World Bank PMU of the Ministry of Welfare carried out as a repeated questionnaire-based survey of nutritional habits beginning in spring 1997 (the same 3 000 respondents interviewed on several occasions) estimated the prevalence of obesity and overweight was 39% for the population[16]. Obviously, the situation in Hungary was optimistic with the declined prevalence of obesity and overweight. But in the report of National Health Interview Survey 2003, 29% of female and 38% of male are overweight, whereas 1 out of 5 adults qualifies as obese, the prevalence of obesity among men aged 65 and over has almost doubled to 30% from its 2000 value of 17%[17].
As a result, the findings in this study are similar with the study of Dr Wang Huijun, and Zhai Fengying, they also applied the new definition of BMI 24 and 28 as the cut-off point for overweight and obesity. They used the data from 1989,1991,1993,1997 and 2000 Chinese Nutrition and Health Survey, the longitudinal survey was conducted by the cooperation with the Carolina Population Center at the University of North Carolina, the National Institute of Nutrition and Food Safety, and the Chinese Center for Disease Control and Prevention coordinated by Pro. Popkin.The subjects were aged 18~45 adults, revealed that the overweight prevalence of both male and female elevated dramatically in the period of 1989~2000, for male from 11.9% to 27.9%, increase 16% in this eleven years, for female from 17.7% to 28.5%, increased 10.8%.The magnitude of overweight in male is wider than that in female, the relative older age groups were higher than younger groups, the prevalence was difference by variation of area, for male in urban area the overweight prevalence was apparently higher than that in rural place, for female in young age group the prevalence in urban is lower than that in rural place, in older age group the profile was contrary[4].
Until now the overall impression of the overweight or obesity is in our mind, I try to clarify the real causation of the epidemic worldwide particular for Qingdao region. Focusing on etiologic factors, the National Institute of Health,USA claimed that obesity is a complex multifactorial chronic disease that develops from an interaction of genotype and the environment[18].Highlighting the environment determinants in my opinion that excess fat intake and commuting physical activity played an important role in the etiology of the obesity epidemic. The daily consumption of animal products for the urban and rural residents has increased from 210 grams and 69 grams respectively in 1992 to 248 grams and 126 grams in 2002, the daily consumption of oils among urban residents increased to 44 grams from 37 grams in 1992. According to the 1982,1992 and 2002 nutrition survey reports, the China average fat intake per day increased from 48.1 g in 1982 to 58.3 g in 1992, then to 76.2 g in 2002 (Table 3). In Qingdao region the figure reached to 90.8 g in 2002 survey, this probably is a good explanation for why Qingdao has a higher prevalence on obesity compare with national average level. In this study the overweight and obesity prevalence of Qingdao people are 39.6% and 18.8% respectively, in the report of China Health and Nutrition Survey 2002, the Chinese adults prevalence of overweight and obesity was 22.8% and 7.1% respectively, while in big city the figure were 30.0% and 12.3% respectively, which was dramatically higher than the overall national level.
Even though there were different of opinions about whether the percentage of dietary fat plays an important role in the rising prevalence of overweight and obesity. We believe that ample research from animal and clinical studies, from controlled trials, and from epidemiological and ecological analyses provided strong evidence that dietary fat plays a role in the development and treatment of obesity. A reduction in fat intake reduces the gap between total energy intake and total energy expenditure and thus an effective strategy for reducing the present epidemic of obesity worldwide. In Pro.Popkin' s study showed that reduction of 10% in the proportion of energy from fat was associated with a reduction in weight of 16 g/d[19].
Table 3 1982,1992 and 2002 national average nutrients intake by urban & rural population in China (reference person/day)
Note:A reference person = 18 years old man who performs physical activity
Data from Ministry of Health,China
Changes in dietary composition, which correspond to socioeconomic growth, may accelerate the prevalence of obesity in China. The composition of the Chinese diet has been shifting towards a larger quantity of animal products, a higher fat intake, and lowers in carbohydrates and fiber[20]. Diet is becoming an increasingly important determinant of body weight in China population, where fat and energy consumption has been increasing steadily during the past decade. Change in fat intake was positively associated with change in BMI in men, and change in physical activity level was inversely associated with change in BMI in women. Energy intake, physical activity and major socio-economic factors were related to BMI in cross-sectional analysis[21]. For males, energy intake below 95% of the Chinese RDA was associated with significantly smaller gains in circumference (WC) and greater loss of mid arm muscle area (MAMA) than energy intake between 95%~125% RDA. For both sexes, protein intake below 10.4% of energy was associated with significantly greater loss of MAMA than intake between 10.4%~12.1% of energy. For females, energy intake above 125% RDA was associated with significantly greater gains in body fat than intake between 95%~125%[22]. According to the findings of Qingdao survey 2002, residents energy intake contribution from fat had reached 35.3 %, exceeding the upper limit of 30 % recommended by the World Health Organization. The situation was more serious in the urban area, this maybe the reasonable explanation of why the prevalence of overweight or obesity is high dramatically in the urban population. In another study of Pro.Popkin present a similar result, among the Chinese adults, dietary energy and fat intakes were positively and significantly associated with the BMI. Household income and physical activity level were also significantly associated with BMI in urban residence and higher incomes were associated with lower energy intake, higher fat intake, and lower physical activity level compared to rural residents and other income categories[23]. Additionally, decreased level of physical activity and leisure are linked to increases in the prevalence of an overweight condition, obesity and diet-related non-communicable diseases [24] In summary, numerous reliable research study convinced that the dietary nutrition transition in terms of more over fat consumption as well as commuting physical activity are strongly associated with the overweight or obesity epidemic.
In this study took the overweight and obesity as the explanatory variables, certain unhealthy conditions as outcome variables, the results indicated that the overweight and obesity were more likely become unhealthy status. If we altered the perspective, taking the unhealthy conditions as explanatory variable, overweight and obesity as outcome variables, again the individuals with unhealthy conditions were more likely gain excess adipose. Those kinds of relationships were illustrated by tremendous studies in different countries. Obesity was significantly associated with a history of diabetes mellitus (18% vs 7%,P<0.05) and hypertension (48% vs 28%,P<0.05). Compared to the non-obese, those who were obese had a higher level of serum uric acid [(311 ± 102)mol/L vs (280 ± 96) mol/L,P<0.05 ]and triglyceride [(2.67± 1.95)mol/L vs (1.86 ± 0.95) mmol/L,P<0.05]. The high prevalence of obesity both in elderly men and women and its strong association with chronic diseases causes economical and social burden for Hungary[25].The results in this study are very close to the Korean statement, in the 1998 Korea Health and Nutrition Examination Survey, which reported that the prevalence of diabetes, hypertension, and dyslipidemia has doubled at a BMI of 23.0 to 24.0 and tripled at a BMI of 26.0 in the Korean adult population. The authors propose that body fat distribution at a BMI of 23.0 in Asians may be similar to those in whites at a BMI of 25.0[26].In another study focusing to older Japanese Americans, multiple regression analysis was performed, controlling for factors known to influence blood pressure values, including age, physical activity index, alcohol intake, current smoking status, and diabetes mellitus. The association between BMI and both systolic and diastolic pressures remained highly statistically significant in these analyses. These results show that obesity and high blood pressure continue to be highly correlated even in old age and suggest that it may be possible to modify incidence of hypertension by changes in body weight[27].A follow up study from 12 Chinese Provinces showed that the prevalence of diabetes in both males and females with BMI>24 and >28 were 23.2% and 18.5% respectively compared with normal body weight were 4.08% and 3.66%[6].Apparently, those series of clinic manifestations developed simultaneously and promoted each other, and presented the common profiles related to metabolic disorders influenced by endocrine system. Obesity is the tip of the iceberg of a cluster of cardiovascular disease risk factors, including hypertension, diabetes, and dyslipidemia, otherwise known as the “Metabolic Syndrome”, “New World Syndrome”, or “Deadly Quartet”. This natural consequence will be an epidemic of cardiovascular complications, such as coronary heart disease and stroke as well as microvascular complications. In the famous Framingham study, 5,209 subjects for both gender were followed for 26 years, using multiple logistic regression to analysis, the obesity was the independent risk factor for cardiovascular disease in both gender[28].Obesity, hyperinsulinaemia, and insulin resistance are characteristic features of Hong Kong Chinese patients who have various component of the metabolic syndrome. There was an increased risk of 3.1 and 5 times when the body BMI was 23.0~24.9 and ≥25, respectively[29].Another crucial evidence also strongly supports the theory that the Metabolic Syndrome is recognized as a high risk factor to CVD. According to WHO MONICA China section report the coronary heart disease incidence increased by 67% between 1984~1997 in male, the average increase was 2.1% annually (P<0.05). We should pay more attention to the report findings,as the incidence of coronary heart disease in Qingdao region was the highest for males figured 108.7/100 000 compared with the lowest one in Anhui Tuzhou region figured 3.3/100 000, the variation between two region was 32.9 times[30].Again the only reasonable explanation is that the risk factors of obesity epidemic in Qingdao region are significantly higher than that in other regions. Let us see the issue from the opposite perspective, if we had controlled the risk factors of Metabolic Syndrome successfully, whether the incidence of CHD will be declined or not. The North Karelia project pilot for Finland from 1972 to 1997 presented the positive answer, as a result of preventive activity, the total mortality decreased by 49%, CVD mortality decreased by 68%, CHD mortality decreased by 73%, in the 35~64 age group in both gender. Therefore this study provides the scientific evidence supports the point that the fatty dietary habits extensively contribute to the Metabolic Syndrome by environmental aspect.
The limitation of this study is that there are some confounders such as the age, socioeconomic status, location, alcohol consumption and level of physical activity, which can distort the associations between the exposure and the outcome. The multiple logistic regression molds should be formulated in a way to control the confounders in the future research study. Further investigations using analytical epidemiological methodology should be carried out to examine the hypothesis whether the over nutrition diet lead to overweight or obesity in diverse populations and areas. The accurate measurement of diet composition is extremely essential to determine the relations between unbalanced nutrition and obesity.
By conclusion, the present study indicates that overweight and obesity are emerging public health problems with an alarming rate in Qingdao region as well as nationwide in China. If no effective strategies or programs will be established to fight and control the risk factors, including obesity, diabetes, hypertension, dyslipidemia, the obesity-related non communicable diseases will be prevalent in the near future and will elevate the socioeconomic burden dramatically. My personal view is that our municipal public health agency should refer to the experiences in the North Karelia Project for formulating the proposal of Healthy City Programm. Governments at all levels are called to strengthen public education, health promotion activities and advocate a balanced diet and a healthy lifestyle. Surveillance and intervention programs to modify the risk factors should be appropriately implemented by community level, meanwhile we should evaluated our strategies or programs with epidemical analytical approaches and follow the cost-effective principles. To improve the situation, the government should ensure to implement laws and regulations concerning nutrition, such as requiring certification of nutritionists and nutritional content of foods such as policosanol, plant stanols, soy isoflavones, omega-3 fatty acids[31].A national scientific diet intake guideline based on nutrition science evidences should also be established and available, to provide authoritative information so that the public can choose food and do physical exercise scientifically. China will also enhance guidance in agriculture and food production, distribution and marketing to help improving people's nutrition and health.
Acknowledgement
I would like to express my deepest gratitude for Pro. Zengchang Pang the director of Qingdao Center for Disease Control and Prevention for his kindly providing the Survey data and allowing me work in Center temporarily. The Dr. Shaojie Wang and Dr. Xiaorong Chen also raised helpful comments on how to extract the case number from the database. My supervisor Dr.Bardors also delivered me many valuable advices and suggestions on how to use survey data design my study.
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(Editor Jaque )(TIAN Tao1，Bárdos Helga2,A)