The research was conducted at the Keck School of Medicine at the University of Southern California to examine the odds of overweight and related correlates in Chinese adolescents.
“In contrast to most findings in studies carried out in Western cultures, we found that frequent consumption of vegetables was actually related to greater odds of overweight in Chinese youth,” the researchers said.
“Diets rich in fruits and vegetables have generally associated with lower caloric intake in studies conducted in the West. However, our findings might be explained by differences in cooking methods,” the researchers said.
According to the researchers, in China, the two most common methods of cooking vegetables are deep-frying and stir-frying, both of which involve generous use of oil, which could result in higher intake of energy.
The study is published in the July 2011 issue of the American Journal of Health Behavior.
The cross-sectional data was collected from a baseline survey in seven cities across China, where a total of 9,023 students and their parents filled out questionnaires prepared by the researchers.
The questionnaires asked vital questions of the sampled respondents regarding their sedentary behaviour, physical activity, sleep duration, self perception, age and school level, BMI and weight status, parental income and education levels.
Under the survey, researchers measured dietary intake during the last month by food frequency items. Five food items were included in the current analyses to assess the consumption of different foods.
This included vegetable intake (fresh or cooked vegetables), fruit intake (fresh fruits including fruit juice), sweets intake (desserts, ice cream, candy, or soda), snack intake (potato chips, corn chips, and tortilla chips), and fast food intake (McDonald’s, KFC, Pizza Hut etc).
Researchers found that mean frequency of vegetable consumption per week during the past 30 days for the sampled respondent was 7.54 times; fruit, 6.50 times; sweets, 4.06 times; snack, 3.11 times; and fast food, 0.43 times.
The researchers further found that those who were overweight consumed vegetables and fruits more frequently, and consumed sweets, snacks, and fast foods less frequently when compared to those who were not overweight.
“Interestingly, we also found that overweight Chinese youth reported a lower frequency of sweets intake and fast food intake,” they said.
The traditional Chinese diet consists of a variety of high-glycemic carbohydrates with rice as the staple grain, they added, which favors weight gain and obesity.
Overweight youth might be consuming greater amounts of foods (rice and noodles) associated with increased caloric intake and increased adiposity, according to them.
“However, intake of these high-glycemic and possibly obesogenic foods was not measured in the current study. In addition, information related to portion size was not collected, which might be another crucial determinant,” they said.
Another potential explanation is that overweight youth might tend to underreport their intake of sweets and fast food, types of high-energy-dense foods, due to social desirability, the report said.
Source American Journal of Health Behavior
Volume 35, Number 4, July 2011 , pp. 438-446(9)
"Correlates of Overweight Status in Chinese Youth: An East-West Paradox"
Authors: Hsu, Ya-Wen; Johnson, C. Anderson; Chou, Chih-Ping; Unger, Jennifer B.; Sun, Ping; Xie, Bin; Palmer, Paula H.; Gallaher, Peggy E.; Spruijt-Metz, Donna