Low-carbohydrate vegan diets in diabetes for weight loss and sustainability: a randomized controlled trial

Abstract

Background: Low-carbohydrate, high animal fat and protein diets have been promoted for weight loss and diabetes treatment. We therefore tested the effect of a low-carbohydrate vegan diet in diabetes as a potentially healthier and more ecologically sustainable low-carbohydrate option. Objectives: We sought to compare the effectiveness of a low-carbohydrate vegan diet with a moderate-carbohydrate vegetarian diet on weight loss and metabolic measures in diabetes. Methods: One hundred and sixty-four male and female participants with type 2 diabetes were randomly assigned to advice on either a low-carbohydrate vegan diet, high in canola oil and plant proteins, or a vegetarian therapeutic diet, for 3 mo, with both diets recommended at 60% of calorie requirements. Body weight, fasting blood, blood pressure, and 7-d food records, to estimate potential greenhouse gas emissions, were obtained throughout the study with tests of cholesterol absorption undertaken at baseline and end of study on 50 participants. Results: Both low-carbohydrate vegan and vegetarian diets similarly but markedly reduced body weight (-5.9 kg; 95% CI: -6.5, -5.28 kg; and -5.23 kg; 95% CI: -5.84, -4.62 kg), glycated hemoglobin (-0.99%; 95% CI: -1.07, -0.9%; and -0.88%; 95% CI: -0.97, -0.8%), systolic blood pressure (-4 mmHg; 95% CI: -7, -2 mmHg; and -6 mmHg; 95% CI: -8, -3 mmHg), and potential greenhouse gas emissions, but only for potential greenhouse gas emissions was there a significant treatment difference of -0.63 kgCO2/d (95% CI: -0.99, -0.27 kgCO2/d) favoring the low-carbohydrate vegan diet. Conclusions: Low-carbohydrate vegan and vegetarian diets reduced body weight, improved glycemic control and blood pressure, but the more plant-based diet had greater potential reduction in greenhouse gas emissions.