Huang’s review includes twelve randomized controlled trials, involving 1, 151 dieters who followed a specific eating regime for between nine and 74 weeks. It is the first study to combine the findings from various independent projects that weighed up the results of vegetarian diets against other eating plans. These include the Atkins diet, and ones recommended by the American Diabetes Association or the US National Cholesterol Education Program.
Overall, individuals assigned to the vegetarian diet groups lost significantly more weight, around 2.02 kg /4.45 pounds, than dieters who ate meat and other animal products. Vegetarians who followed a vegan diet lost even more weight. Comparatively, they lost around 2.52 kg / 5.55 pound, more than non-vegetarian dieters. Vegetarians who do consume dairy products and eggs lost around 1.48 kg/3.26 pounds, more than those on a non-vegetarian diet. People following vegetarian diets that prescribe a lower than normal intake of calories (so-called energy restriction) also shed more kilograms than those without any such limitations being placed on their eating habits.
According to Huang, the abundant intake of whole grains, fruits and vegetables might play a role in the favorable results seen in vegetarian diets. Whole-grain products and vegetables generally have low glycemic index values and don’t cause blood sugar levels to spike. Fruits are rich in fiber, antioxidants, minerals and protective chemicals that naturally occur in plants. Whole-grain products contain soluble fiber. Such so-called good fiber helps to delay the speed by which food leaves the stomach and ensures good digestion. It also allows enough nutrients to be absorbed while food moves through the intestines. Several studies have reported that fiber consumption helps with weight loss.
“Vegetarian diets are more effective than non-vegetarian diets for weight loss, ” says Huang, who added that longer term intervention trials are needed to investigate the effect of vegetarian diets on weight control and cardio-metabolic risk.