According to a meta-analysis of eleven randomized trials that involved approximately 800 individuals older than 18 years, a twelve-week vegan diet could result in weight loss and improve blood sugar control in overweight individuals as well as individuals with type 2 diabetes.
Vegan diets rich in veggies, fruits, nuts, seeds, and legumes without any animal-derived foods, didn't however have an impact on triglycerides or blood pressure in comparison to other diets.
The researchers carried out a systematic review and meta-analysis of all relevant randomized trials, comparing the impact of vegan diets to other kinds of diets on cardiometabolic risk factors which included systolic and diastolic blood pressure, blood sugar levels, BMI, body weight, LDL cholesterol, HDL cholesterol, total cholesterol, and triglycerides.
Vegan diet comparisons were made with either passive control groups consisting of individuals continuing normal diet without any changes or active control groups consisting of individuals following other dietary interventions which included portion-controlled diets, various diabetes diets, or Mediterranean diets.
Data were analyzed for eleven studies that involved 796 individuals with an average age of between 48 and 61 who had type 2 diabetes or were overweight with a BMI of 25 kg/m2 or more. The trials lasted for a minimum of twelve weeks with an average duration of nineteen weeks and weight loss of a minimum of 11lbs was considered clinically meaningful.
Analyses revealed that vegan diets reduced body weight significantly compared to control diets. But the effects on blood sugar level, total cholesterol, and LDL cholesterol were quite small.
Further analyses revealed even greater BMI and body weight reductions when vegan diets were compared to maintaining a normal diet with no changes than compared to other intervention diets.
According to the researchers, this thorough assessment of the evidence suggests with reasonable certainty that sticking to a vegan diet for a minimum of twelve weeks could lead to clinically meaningful weight loss and improve blood sugar levels, and could therefore be used for managing type 2 diabetes and overweight. Vegan diets likely result in weight loss because they are linked to a reduced calorie intake as a result of a lower fat content and higher dietary fiber content.
The researchers point out some caveats to the results, including most of the studies' small sample sizes, and that there was a substantial variation in vegan diets by fat, protein, and carbohydrate content, and a control diet was not prescribed in any of the studies that matched the intervention diet exactly in all other aspects other than veganism. The effects of vegan interventions on cardiometabolic health may therefore partly be caused by macronutrient composition differences and energy intake between the groups.
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