Determinants of long-term weight change among middle-aged Swedish women

Objective: To describe the determinants of 12-year weight change among middle-aged women in Sweden. Methods: In 1991/1992, 49,259 women across Sweden were recruited into a cohort. In 2003, 34,402 (73%) completed follow-up. Lifestyle and health characteristics including weight were collected, and 12-year weight change and substantial weight gain (≥+5.0 kg) were calculated; association between baseline characteristics and odds ratios (OR) with 95% confidence intervals (CI) of substantial weight gain were estimated. Results: During the 12-year follow-up, 81% of women experienced weight gain. Being above average weight (64.5 kg) at baseline (OR =1.20, 95% CI: 1.14–1.26) and smoking 1 to 9 (OR = 1.10, 95% CI: 1.01–1.20), 10 to 19 (OR = 1.30, 95% CI: 1.21–1.39), or ≥20 cigarettes daily (OR = 1.17, 95% CI: 1.04–1.32) increased a woman's odds of experiencing substantial weight gain (influenced by smoking cessation). In contrast, risk of substantial weight gain was reduced among women 45 to 50 years of age (OR = 0.79, 95% CI: 0.73–0.85), women reporting high alcohol consumption (OR = 0.90, 95% CI: 0.83–0.98), and those with medium (OR = 0.93, 95% CI: 0.87–1.00) or high (OR 0.83, 95% CI: 0.77–0.90) physical activity levels. Conclusions: The majority of women experienced weight gain during middle age. Population-specific determinants of weight gain should guide obesity prevention efforts.