Background: Observational studies suggest that a plant-based diet is inversely related to body mass index (BMI), overweight, and obesity.
Objective: Our objective was to examine the BMI (kg/m(2)) and risk of overweight and obesity of self-defined semivegetarian, lactovegetarian, and vegan women.
Design: Data analyzed in this cross-sectional study were from 55459 healthy women participating in the Swedish Mammography Cohort. Women were asked whether they considered themselves to be omnivores (n = 54257), semivegetarians (n = 960), lactovegetarians (n = 159), or vegans (n = 83), and this question was the main exposure variable in this study. In secondary analyses, we reclassified women as lactovegetarians on the basis of food intakes reported on the food-frequency questionnaire.
Results: The prevalence of overweight or obesity (BMI >/= 25) was 40% among omnivores, 29% among both semivegetarians and vegans, and 25% among lactovegetarians. In multivariate, adjusted logistic regression analyses, self-identified vegans had a significantly lower risk of overweight or obesity [odds ratio (OR) = 0.35; 95% CI: 0.18, 0.69] than did omnivores, as did lactovegetarians (OR = 0.54; 95% CI: 0.35, 0.85) and semivegetarians (OR = 0.52; 95% CI: 0.43, 0.62). Risk of overweight or obesity remained significantly lower among lactovegetarians classified on the basis of the food-frequency questionnaire (OR = 0.48; 95% CI: 0.30, 0.78).
Conclusions: Even if vegetarians consume some animal products, our results suggest that self-identified semivegetarian, lactovegetarian, and vegan women have a lower risk of overweight and obesity than do omnivorous women. The advice to consume more plant foods and less animal products may help individuals control their weight.