Age-dependent changes in the risk of weight gain in Chinese adults: results from the Kailuan cohort study.

OBJECTIVES

Over the past decades, China has seen a dramatic epidemic of overweight and obesity. However, the optimal period for interventions to prevent overweight/obesity in adulthood remains unclear, and little is known regarding the joint effect of sociodemographic factors on weight gain. We aimed to investigate the associations of weight gain with sociodemographic factors, including age, sex, educational level, and income.

STUDY DESIGN

This was a longitudinal cohort study.

METHODS

This study included 121,865 participants aged 18-74 years from the Kailuan study who attended health examinations over the period 2006-2019. Multivariate logistic regression and restricted cubic spline were used to evaluate the associations of sociodemographic factors with body mass index (BMI) category transitions over two, six, and 10 years.

RESULTS

In the analysis of 10-year BMI changes, the youngest age group had the highest risks of shifting to higher BMI categories, with odds ratio of 2.42 (95% confidence interval 2.12-2.77) for a transition from underweight or normal weight to overweight or obesity and 2.85 (95% confidence interval 2.17-3.75) for a transition from overweight to obesity. Compared with baseline age, education level was less related to these changes, whereas gender and income were not significantly associated with these transitions. Restricted cubic spline analyses suggested reverse J-shaped associations of age with these transitions.

CONCLUSIONS

The risk of weight gain in Chinese adults is age dependent, and clear public healthcare messaging is needed for young adults who are at the highest risk of weight gain.