" The main finding was that vegan and lacto-ovo vegetarian diets were associated with a nearly one-half reduction in risk of type 2 diabetes compared with the risk associated with nonvegetarian diets after adjustment for a number of socioeconomic and lifestyle factors, as well as low BMI, that are typically associated with vegetarianism. Pesco- and semi-vegetarian diets were associated with intermediate risk reductions: between one-third and one-quarter. These data indicate that vegetarian diets may in part counteract the environmental forces leading to obesity and increased rates of type 2 diabetes, though only vegan diets were associated with a BMI in the optimal range. Inclusion of meat, meat products, and fish in the diet, even on a less than weekly basis, seems to limit some of the protection associated with a vegan or lacto-ovo vegetarian diet. These findings may be explained by adverse effects of meat and fish, protective effects of typical constituents of vegan and lacto-ovo vegetarian diets, other characteristics of people who choose vegetarian diets, or a combination of these factors. "

― Serena Tonstad