Vegetarian Diets Improve Weight and Glucose, But Not Anthropometric Outcomes

Vegetarian diets alone may not improve blood pressure and anthropometric outcomes in patients with overweight and obesity.

Vegetarian diets can reduce weight and glucose compared with omnivorous diets, according to a systematic review and meta-analysis published in the International Journal of Obesity. However, adherence to a vegetarian diet may not improve body mass index (BMI), waist and hip circumference, hemoglobin A1c (HbA1c) levels, or blood pressure, the report shows.

Researchers included data from 9 randomized controlled trials that evaluated the effects of a vegetarian diet on metabolic, anthropometric, or blood pressure outcomes vs an omnivorous diet in individuals with overweight (25-30 kg/m2) or obesity (>30 kg/m2) during a mean 7.6-month period. Among the included studies, 4 assessed lacto-ovo-vegetarian diets and 5 examined vegan diets. Primary outcomes were weight, BMI, waist and hip circumference, and body fat percentage, while secondary outcomes included fasting serum glucose, Hb1Ac, and insulin levels, and blood pressure.   

In comparison to an omnivorous diet, VDs may reduce weight and glucose but the evidence is very uncertain.

The study determined that vegetarian diets decreased weight (mean difference [MD], −3.60 kg; 95% CI, −4.75 to −2.46) and glucose (MD, −10.64 mg/dL; 95% CI, −15.77 to −5.51), compared with an omnivorous diet. However, it did not significantly decrease BMI (MD, −0.87 kg/m2; 95% CI, −1.80 to 0.06), waist circumference (MD, −3.00 cm; 95% CI, −6.20 to 0.20), hip circumference (MD, −0.86 cm; 95% CI, −3.46 to 1.74), HbA1c levels (MD, −0.40%; 95% CI, −0.89 to 0.10) or insulin levels (MD, −3.83 mU/L; 95% CI, −8.06 to 0.40) compared with an omnivorous diet. 

Vegetarian diet also did not significantly affect systolic or diastolic blood pressure compared with omnivorous diets (MD, −0.25 mm Hg; 95% CI −2.58 to 2.07 and MD, −1.57 mm Hg; 95% CI −3.93 to 0.78, respectively).

“In comparison to an omnivorous diet, [vegetarian diets] may reduce weight and glucose but the evidence is very uncertain,” according to the study authors.

Study limitations include a low quality of evidence, difference in control diets between studies, and a short follow-up duration.

This article originally appeared on Endocrinology Advisor


Melgar B, Diaz-Arocutipa C, Huerta-Rengifo C, Piscoya A, Barboza JJ, Hernandez AV. Vegetarian diets on anthropometric, metabolic and blood pressure outcomes in people with overweight and obesity: a systematic review and meta-analysis of randomized controlled trials. Int J Obes (Lond). Published online August 1, 2023. doi:10.1038/s41366-023-01357-7