OBJECTIVE: We evaluated the prevalence of obesity in relation to adherence to a Mediterranean diet. METHODS: We conducted a cross-sectional survey that randomly enrolled 1514 men (18 to 87 y old) and 1528 women (18 to 89 y old) with no history of cardiovascular disease. Anthropometric indices were measured and frequency of various foods consumed during a usual week was recorded. Adherence to a Mediterranean diet was assessed by a diet score that incorporated the inherent characteristics of this diet. RESULTS: Prevalences of overweight and obesity were 53% and 20% in men and 31% and 15% in women. An inverse relation was observed between diet score, waist-to-hip ratio (r = -0.31, P < 0.001), and body mass index (r = -0.4, P < 0.001) after adjusting for sex and age. Greater adherence to the Mediterranean diet (i.e., highest tertile) was associated with a 51% lower odds of being obese (odds ratio 0.49, 95% confidence interval 0.42 to 0.56) and a 59% lower odds of having central obesity (odds ratio 0.41, 95% confidence 0.35 to 0.47) compared with a non-Mediterranean diet (i.e., lowest tertile) after controlling for age, sex, physical activity status, metabolism, and other variables. CONCLUSION: We observed an inverse relation between adherence to a Mediterranean dietary pattern and prevalence of obesity in a free-eating, population-based sample of men and women, irrespective of various potential confounders.