Transitioning to plant-based diets may lead to greater increases in fiber [6–8], with high-fiber diets being associated with lower body weights in epidemiologic studies [9], and greater decreases in dietary fat [6–8], with studies showing that low-fat diets are associated with weight loss [10]. Because of these potential changes in nutrients among groups, we hypothesized that differences in weight loss would follow similar pat- terns seen in epidemiologic studies with weight loss being incrementally greater along the plant-based dietary spectrum from omni to semi-veg to pesco-veg to veg to vegan diets. Furthermore, we hypothesized that the vegan group would have significantly greater weight loss compared with the pesco-veg, semi-veg, and omni groups.