Type of vegetarian diet, body weight, and prevalence of type 2 diabetes

OBJECTIVE - We assessed the prevalence of type 2 diabetes in people following different types of vegetarian diets compared with that in nonvegetarians. RESEARCH DESIGN AND METHODS - The study population comprised 22,434 men and 38,469 women who participated in the Adventist Health Study-2 conducted in 2002-2006. We collected self-reported demographic, anthropometric, medical history, and lifestyle data from Seventh-Day Adventist church members across North America. The type of vegetarian diet was categorized based on a food-frequency questionnaire. We calculated odds ratios (ORs) and 95% CIs using multivariate-adjusted logistic regression. RESULTS - Mean BMI was lowest in vegans (23.6 kg/m2) and incrementally higher in lactoovo vegetarians (25.7 kg/m2), pesco-vegetarians (26.3 kg/m2), semi-vegetarians (27.3 kg/m2), and nonvegetarians (28.8 kg/m 2). Prevalence of type 2 diabetes increased from 2.9% in vegans to 7.6% in nonvegetarians; the prevalence was intermediate in participants consuming lacto-ovo (3.2%), pesco (4.8%), or semi-vegetarian (6.1%) diets. After adjustment for age, sex, ethnicity, education, income, physical activity, television watching, sleep habits, alcohol use, and BMI, vegans (OR 0.51 [95% CI 0.40-0.66]), lacto-ovo vegetarians (0.54 [0.49-0.60]), pescovegetarians (0.70 [0.61- 0.80]), and semi-vegetarians (0.76 [0.65- 0.90]) had a lower risk of type 2 diabetes than nonvegetarians. CONCLUSIONS - The 5-unit BMI difference between vegans and nonvegetarians indicates a substantial potential of vegetarianism to protect against obesity. Increased conformity to vegetarian diets protected against risk of type 2 diabetes after lifestyle characteristics and BMI were taken into account. Pesco- and semi-vegetarian diets afforded intermediate protection. © 2009 by the American Diabetes Association.