Why do some overweight children remain overweight, whereas others do not?

Objective: To study the dynamics of childhood overweight and the influence of dietary intake on tracking of overweight. Design and setting: A follow-up study conducted in China. Subjects: Ninety-five overweight children, 6-13 years old, identified from 1455 children at baseline, were followed over a 2-year period. Methods: Data on anthropometry and 3-day dietary intake were collected at baseline and during follow-up. Overweight was defined using the International Obesity Task Force reference of body mass index (BMI)-for-age. Differences between groups were tested using analysis of variance and Cochran-Mantel-Haenszel tests. Results: Of the 95 overweight children, 36.8% remained overweight 2 years later ('tracking group'). Urban boys were three times more likely than rural boys to remain overweight (63.2% vs. 21.9%). At baseline, the tracking group had higher BMI, body weight and fat intake (% of energy), and lower carbohydrate intake (% of energy), than the non-tracking group (who shifted from overweight to not overweight); they were more likely to have a high-fat or high-meat diet, but less likely to have a diet high in carbohydrate or vegetables and fruit. During the follow-up, the tracking group increased fat intake and reduced carbohydrate intake while the non-tracking group did not; and they also grew slower in height but faster in weight. Tracking of overweight seemed to be related to tracking of high-meat (relative risk (RR) 2.4, 95% confidence interval (CI) 1.0-5.6, P < 0.05) and high-fat (RR 1.5, 95% CI 0.9-2.5, P < 0.1) diets. Conclusion: Considerable changes in children's overweight status during childhood and adolescence were observed in China, a transitional society. Dietary patterns, particularly dietary composition, seemed to influence the tracking patterns of overweight.