Modeling the effect of diet and physical activity on body mass index in prepregnant and postpartum women.

Objectives: This study aimed to assess, using simulation modeling, the theoretical effect of key diet and physical activity (PA) modification scenarios could have on body mass index (BMI) in prepregnant and postpartum women.

Methods: Simulation modeling using data from the 2011 to 2012 National Nutrition and Physical Activity Survey was performed for a subsample of prepregnant and postpartum women. The regression coefficients for each diet and PA component from multivariable linear regression equations for BMI were used to calculate a predicted BMI. Scenario modeling using a moderation approach was applied to targeted diet and PA components for the entire sample and subgroups of populations of women who failed to meet dietary and PA recommendations and among the lowest socioeconomic groups.

Results: In prepregnancy and postpartum scenarios, respectively, increasing whole grains by 2 to 3 servings/d reduced BMI by 1.16 and 0.85 kg/m. For postpartum women, BMI was reduced by 0.28 kg/m for every 5-g/d increase in fiber intake. A 480- and 540-min/wk increase in PA resulted in average BMI reductions of 0.95 and 1.19 kg/m in prepregnant and postpartum women, respectively. A similar pattern of theoretical reductions in BMI was observed with increased whole grains, fiber, and PA among the most disadvantaged socioeconomic groups of women.

Conclusions: Increasing intake of whole grains by 2 to 3 servings/d could result in reductions in BMI of 1.16 and 0.85 kg/m, and a 480- and 540-min/wk increase in PA could result in BMI reduction of 0.95 and 1.19 kg/m in prepregnant and postpartum women, respectively. This provides an evidence base to guide tailored nutrition messaging for obesity prevention efforts in reproductive age women.