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XA0404145 RISK FACTORS FOR OBESITY IN CHINESE ADULTS GuANsHENG MA, M.D. Institute of Nutrition and Food Safety, Chinese Center for Disease Control and Prevention 1. SCIENTIFIC BACKGROUND AND SCOPE OF TE PROJECT 1.1. Demographic Transition in China The World Health Report draws attention to the fact that this is an era of population aging. China is also becoming a society of aging. The total population in China is 12 billion which almost one-fourth of the world population in 1997 [1]. There were more than 0.1 billion population aged 65 and over in 1996, which 6 of the total population in China and about 20% of the total aging population in the world 1]. Along with the development of socioeconomic, improvement of living standard and health care system, the death rate decreased gradually since 1960 [1] while the life expectancy increased dramatically since 1949. The life expectancy at birth for Chinese people was 35.6 years before 1949. It increased to 68.9 years, 71.0 years in 1985, 1997 respectively 2. However, increases in life expectancy mean little if health expectancy is not assured simultaneously. 1.2. Nutritional and Epidemiological Transitions in China The pattern of food consumption in China has been subject to significant changes in the last 30-40 years. According to the national statistical of food provision, while the consumption of plant foods decreased, consumption of animal foods increased significantly from 1977-1987 [3] and the same trend continues 4 This change is more significant in urban areas as compared with rural areas. There is also a shift of disease pattern along with the change of dietary pattern. Health statistical data from National Statistics [5] show that in the last four decades, there has been a steep decrease in communicable diseases and simultaneously, a significant increase in degenerative chronic diseases. The mortality rate of acute infectious diseases reduced by 98% between 1957 and 1990, but at the same time, that of cancer, hypertension, coronary heart disease (CHD), and diabetes increased by 240%, 60%, 88%, and 169% respectively. The sum of mortality of cancer, cerebrovascular and cardiovascular diseases now account for about 70% of the total deaths in urban areas, 50% in rural areas in China. All the above data confirm that the transition of the dietary pattern has already affected the health of the Chinese population, especially people in the urban areas. 1.3. Obesity in China China in the early 1980s had the best population distribution of BMIs in the world but major BMI increases are underway, particularly with urbanization. According to results of 1992 China National Nutrition Survey, there were 23. 1% of adults aged 20-45 in urban areas whose BMI bigger than 25 kg/m2. Using the definitions for overweight based on the Body Mass Index 6] almost half of the adult population in Beijing 7] and more than half of the elder 63 population in urban Beijing are overweight [8]. Obesity is now one of the major public health problems in China. The economic costs of obesity are tremendous. In Australia 9], the direct costs of health care attributable to obesity were A$395 million or 2 per cent of health care costs between 1989- 1990. In Netherlands [10], the estimated direct costs associated with overweight and obesity were one billion Dutch guilders per year or 4 per cent of the total health care costs in 1991 In the U.S. [I 1, the estimated direct costs of obesity were 45.8 billion dollars or 68 per cent of the health care costs in 1990. Although no data available about the direct costs of obesity in China, it should be an astronomical figure. Many health hazards are associated with obesity 12]. Being obese can induce multiple metabolic abnormalities that contribute to cardiovascular disease, diabetes mellitus, and other chronic degenerative diseases 13 ]. Manson 14] and Lew [ 15] reported that increased risk of all-cause and coronary heart disease mortality were associated with BMI. Study in USA 16] indicated that obese individuals have a four time greater risk of developing hypertension as compared to lean people. Colditz 17] found that early obesity increased risk of developing non-insulin-dependent diabetes mellitus (NIDDM) and 88 to 97 per cent of NIDDM was attributable to their obesity. The underlying causes of the increasing prevalence of obesity are not well understood, Energy intake and physical activity are thought to be some of the major lifestyle factors that are involved [18, 19]. However, the contribution of each specific factor has not yet been identified. It has been recognized that high levels of body fat cannot have been accumulated without energy intake being unusually high or energy expenditure being unusually low, or a combination of these two options. There have been cross-sectional, prospective and intervention studies in defining factor which primarily determining energy regulation 20-27]. However, the results of these studies are conflicting and have not yet permitted any general consensus over the relative importance of energy intake and energy expenditure in the determination of body fat mass. Further study should be conducted to clarify it. Because effective measures for treating obesity are lacking, the most effective and economic strategy is to prevent it happens. The risk factors to obesity should be identified in order to develop effective prevention strategies. 2. RESEARCH OBJECTIVES • To compare the dietary intakes of Chinese adults with normal weight, overweight and obesity. • To compare the physical activity levels and energy expenditure of Chinese adults with normal weight, overweight and obesity. • To identify the risk factors for overweight and obesity among Chinese population. • To provide scientific information for developing obesity prevention strategies. 64 3. STUDY DESIGN This is a cross-sectional study. One hundred fifty adults were recruited for this study. They were divided into three groups (normal weight, overweight and obesity) according to their 13M[Is. 2 • Normal weight: BNE 18.5-25.0 kg/m • Overweight: BM[I 25.0-29.9 k g/M2 • Obesity: BNH >30.0 kg/M2 4. METHODS 4.1. Body Composition and Energy Expenditure 2-H and 18-0 were used for estimating body composition and total energy expenditure. Using isotope-ratio mass spectrometry according to established protocol performed isotope analyses. 4.2. Physical Activity Physical activity questionnaire was used for collecting physical activity. 4.3. Dietary Intake Three-day (two weekdays and one weekend day) food weighted method was used. The dietary energy and nutrients intakes were calculated by using the 1991 Chinese Food Composition Table. 4.4. Body Fat Distribution Standard procedure was followed to measure subjects'weight, height, circumferences of waist, hip and mid thigh. Waist-to-hip and waist-to-thigh ratio were used as the index of fat distribution. 4.5. Serum Insulin and Leptin Serum insulin and leptin levels were assayed by using Radioimmunoassay. 4.6. Lipid Profile Lipid profile including plasma total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), very low-density lipoprotein VLDL), lipoprotein (a), apolipoprotein (apo) A-I, and apo levels were analyzed in Institute of Nutrition and Food Hygiene by using the established methods. 65 4.7. Blood Pressure Blood pressure was measured on two study mornings with a random-zero sphygmomanometer. Means of measurements on the two study days were used in the analysis. 4.8. Blood Samples A single fasting blood sample of 20 ml was drawn from each subject's vein for preparation of plasma and serum, which then was stored at 80 OC. 5. SCREENING AND RECRUITMENT 5.1. Screening Five hundred adults aged 35-52 years from 24 neighborhood committees in 4 urban districts of Beijing were involved for the screen. A questionnaire was administrated for each of them. The screening data was analyzed, 155 subjects from 500 candidates were qualified for the study. 5.2. Data Collection A 7-day study was conducted involving collecting data on anthropometry, physical activity, and dietary survey in each subject. The general information of the subjects was collected by interview-administered general questionnaire. Body composition was assessed by deuterium oxide dilution technique on study day 1. Physical activity was measured by using the modified VMO 7-day and 1-year questionnaires. Dietary intake was measured by using 3-day food weighted method and food frequency questionnaire. The dietary energy and nutrients intakes were calculated using the 1991 Chinese Food Composition Table. Standard procedure was followed to measure subject's weight, height, circumferences of waist, hip and mid thigh. Blood pressure was measured on the morning of two study days using a standard random-zero mercury sphygmomanometer A single fasting blood sample of 30 ml was drawn from each subject for preparation of plasma and serum. Serum insulin and leptin concentration were analyzed using radioimmunoassay. Lipid profile was analyzed by using standard methods which meet the performance requirements of the lipid standardization program of the CDC. The dietary survey was carried out at subject's home. All other measurements were conducted in the lab of the institute. 66 5.3. Chemical and physical analysis 5.3. 1. Foodsample Gross energy content was determined in freeze-dried samples by using a bomb calorimeter. Total fat content was determined in freeze-dried samples by acid hydrolysis. 5.3.2. Body composition Abundances of deuterium in the isotope dose dilutions and in the urine specimens were analyzed by using isotope-ratio mass spectrometry. 5.3.3. Energy expenditure Energy expenditure was assessed by modified WHO -year questionnaires. 5.3.4. Blood sample Lipid profile including TC, TG, HDL, LDL, VLDL, lipoprotein (a), apo A-1, and apo B concentrations were analyzed by using standard methods which meet the performance requirements of the lipid standardization program of the CDC.

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