Diet quality, physical activity, smoking status, and weight fluctuation are associated with weight change in women and men.

The effect of diet quality on weight change, relative to other body weight determinants, is insufficiently understood. Furthermore, research on long-term weight change in U.S. adults is limited. We evaluated prospectively patterns and predictors of weight change in Framingham Offspring/Spouse (FOS) women and men (n = 1515) aged > or =30 y with BMI > or = 18.5 kg/m2 and without cardiovascular disease, diabetes, and cancer at baseline over a 16-y period. Diet quality was assessed using the validated Framingham Nutritional Risk Score. In women, older age (P < 0.0001) and physical activity (P < 0.05) were associated with lower weight gain. Diet quality interacted with former smoking status (P-interaction = 0.02); former smokers with lower diet quality gained an additional 5.2 kg compared with those with higher diet quality (multivariable-adjusted P-trend = 0.06). Among men, older age (P < 0.0001) and current smoking (P < 0.01) were associated with lower weight gain, and weight fluctuation (P < 0.01) and former smoking status (P < 0.0001) were associated with greater weight gain. Age was the strongest predictor of weight change in both women (partial R(2) = 11%) and men (partial R(2) = 8.6%). Normal- and overweight women gained more than obese women (P < 0.05) and younger adults gained more weight than older adults (P < 0.0001). Patterns and predictors of weight change differ by sex. Age in both sexes and physical activity among women as well as weight fluctuation and smoking status in men were stronger predictors of weight change than diet quality among FOS adults. Women who stopped smoking over follow-up and had poor diet quality gained the most weight. Preventive interventions need to be sex-specific and consider lifestyle factors.