Overweight and obesity and associated health risks have become epidemic in several regions around the world. Numerous studies have addressed the dietary habits of vegetarians and vegans in terms of disease prevention and nutritional deficiencies but the relationship between overweight and obesity and the demographic, psychosocial, lifestyle, and dietary intake of omnivores, vegetarians, and vegans has received less attention. Guided by the social-ecological model, this study included a cross-sectional, quantitative, anonymous web-based survey to obtain dietary information on omnivores, vegetarians, and vegans. Vegans demonstrated a significantly lower mean and median body mass index ( p=0.00) than omnivores, semi-vegetarians, and vegetarians. Multiple logistic regression analysis demonstrated no significant difference in the odds of overweight (OR=0.41; p=1.14) and obesity (OR=0.47; p=0.28) in vegans compared to omnivores. Alcohol was significantly protective against obesity for both 1-2 (OR=0.33; p=0.03) and 3-30 (OR=0.20; p=0.01) days drinking per month while binge drinking significantly increased the odds of obesity (OR=4.44; p=0.01). Multiple logistic regression analysis stratified for levels of exercise revealed an interaction between diet and exercise. A vegan diet was significantly protective against obesity for low-level exercise in terms of frequency (OR=0.31; p=0.02 ) and total minutes per week (OR=0.23; p=0.02) compared to omnivores. Coupled with prior studies these results may contribute to positive social change by facilitating a broad-based paradigm shift in the view of diet and exercise as well as providing evidence that can be implementated in broad-based obesity control programs to reduce the morbidity and mortality associated with obesity.