A Plant-Based High-Carbohydrate, Low-Fat Diet in Overweight Individuals in a 16-Week Randomized Clinical Trial: The Role of Carbohydrates
Physicians Committee for Responsible Medicine, 5100 Wisconsin Ave, N.W. Ste.400, Washington, DC 20016, USA
School of Medicine, University of Utah, Salt Lake City, UT 84132, USA
Adjunct Faculty, George Washington University School of Medicine and Health Sciences, Washington, DC 20016, USA
Author to whom correspondence should be addressed.
Nutrients 2018, 10(9), 1302; https://doi.org/10.3390/nu10091302
Received: 9 August 2018 / Revised: 5 September 2018 / Accepted: 10 September 2018 / Published: 14 September 2018
(This article belongs to the Special Issue Diet and Weight Loss)
The effects of carbohydrates on body weight and insulin sensitivity are controversial. In this 16-week randomized clinical trial, we tested the role of a low-fat, plant-based diet on body weight, body composition and insulin resistance. As a part of this trial, we investigated the role of changes in carbohydrate intake on body composition and insulin resistance. Participants (n = 75) were randomized to follow a plant-based high-carbohydrate, low-fat (vegan) diet (n = 38) or to maintain their current diet (n = 37). Dual-energy X-ray absorptiometry was used to measure body composition. Insulin resistance was assessed with the Homeostasis Model Assessment (HOMA-IR) index. A repeated measure ANOVA model was used to test the between-group differences from baseline to 16 weeks. A linear regression model was used to test the relationship between carbohydrate intake, and body composition and insulin resistance. Weight decreased significantly in the vegan group (treatment effect −6.5 [95% CI −8.9 to −4.1] kg; Gxt, p < 0.001). Fat mass was reduced in the vegan group (treatment effect −4.3 [95% CI −5.4 to −3.2] kg; Gxt, p < 0.001). HOMA-IR was reduced significantly in the vegan group (treatment effect −1.0 [95% CI −1.2 to −0.8]; Gxt, p = 0.004). Changes in consumption of carbohydrate, as a percentage of energy, correlated negatively with changes in BMI (r = −0.53, p < 0.001), fat mass (r = −0.55, p < 0.001), volume of visceral fat (r = −0.35, p = 0.006), and HOMA (r = −0.27, p = 0.04). These associations remained significant after adjustment for energy intake. Changes in consumption of total and insoluble fiber correlated negatively with changes in BMI (r = −0.43, p < 0.001; and r = −0.46, p < 0.001, respectively), fat mass (r = −0.42, p < 0.001; and r = −0.46, p < 0.001, respectively), and volume of visceral fat (r = −0.29, p = 0.03; and r = −0.32, p = 0.01, respectively). The associations between total and insoluble fiber and changes in BMI and fat mass remained significant even after adjustment for energy intake. Increased carbohydrate and fiber intake, as part of a plant-based high-carbohydrate, low-fat diet, are associated with beneficial effects on weight, body composition, and insulin resistance.