Obesity Polygenic Risk and Healthy Lifestyle Interactions on Weight Trajectories in Women and Men

BACKGROUND: Genetics and environmental factors contribute to obesity risk, but the extent to which healthy behaviors can offset genetic susceptibility remains unclear. We examined the interaction between obesity polygenic risk and a composite healthy lifestyle score on body mass index (BMI) trajectories in women and men. METHODS: We analyzed 13 780 women from the Nurses' Health Study and 8242 men from the Health Professionals Follow-Up Study, all of European ancestry and free of major chronic disease at baseline. The lifestyle score comprised American Heart Association Essential 8 components (nonsmoking, physical activity, healthy eating, adequate sleep) plus moderate alcohol intake, modeled as a time-varying variable. A genome-wide polygenic score for BMI was derived from genome-wide association study. Adjusted linear mixed-effects models estimated associations and interactions on biennial BMI measures over up to 26 years. Comparing the healthiest with the least healthy lifestyle groups, genetic effects on BMI were 35% lower in women and 28% lower in men. In sensitivity analyses, higher diet quality and physical activity consistently attenuated genetic associations in both cohorts, whereas current smoking showed similar effects in women only. CONCLUSIONS: Adherence to a healthier lifestyle attenuated the association between obesity polygenic risk and BMI in a dose-response manner.