Association of Adult Weight Gain With Major Health Outcomes Among Middle-aged Chinese Persons With Low Body Weight in Early Adulthood

IMPORTANCE: The association of weight gain from early to middle adulthood with disease risk has not been adequately studied. OBJECTIVE: To investigate the association of adult weight gain with major health outcomes in a Chinese population with low body weight in early adulthood. DESIGN, SETTING, AND PARTICIPANTS: This population-based cohort study assessed data from 48 377 women and 35 989 men aged 40 to 59 years at recruitment in 2 prospective cohort studies in China. The Shanghai Women’s Health Study recruited 74 941 women, aged 40 to 70 years, from January 1, 1996, to December 31, 2000, and the Shanghai Men’s Health Study recruited 61 482 men, aged 40 to 74 years, from January 1, 2002, to December 31, 2006. This analysis was conducted from September 1, 2017, to April 30, 2018. EXPOSURES: Weight gain from 20 years of age to 40 to 59 years of age. MAIN OUTCOMES AND MEASURES: Mortality and incidence of cancers and other chronic diseases. RESULTS: This analysis included 48 377 women (mean [SD] age, 47.8 [5.3] years) and 35 989 men (mean [SD] age, 49.6 [5.1] years). Per 5-kg weight gain from early to middle adulthood was associated with an approximately 10% (hazard ratio [HR], 1.09; 95% CI, 1.04-1.14 for men; HR, 1.14; 95% CI, 1.11-1.19 for women) elevated all-cause mortality and a greater than 20% (HR, 1.26; 95% CI, 1.16-1.38 for men; HR, 1.23; 95% CI, 1.14-1.33 for women) cardiovascular disease–related mortality in later life among individuals who reached a body mass index (BMI) of 23 or higher at middle adulthood. Body mass index at middle adulthood also modified the association of weight gain with risk of obesity-related cancers, with weight gain of 20 kg or more associated with increased risks both for men (HR, 1.34; 95% CI, 1.07-1.67) and for women (HR 1.45; 95% CI, 1.24-1.68). No similar associations were found for individuals with a BMI of 18.5 to 22.9. Regardless of BMI, weight gain was associated with elevated risks of type 2 diabetes, hypertension, fatty liver disease, stroke, gout, and gallstones, particularly for type 2 diabetes (HR, 7.87; 95% CI, 6.91-8.97 for women; HR, 4.95; 95% CI, 4.23-5.79 for men) and fatty liver disease (HR, 3.68; 95% CI, 3.42-3.95 for women; HR, 2.83, 95% CI, 2.56-3.13 for men) in individuals with weight gain of 20 kg or more compared with those with a healthy weight. CONCLUSIONS AND RELEVANCE: This study found that weight gain from early to middle adulthood was associated with disease incidence and mortality in later life. The BMI at middle adulthood modified the association of weight gain with mortality and cancer incidence but not risk of other major chronic diseases.