Plain language summary
Suboptimal nutrition is a major cause of obesity, chronic disease, and premature death across the nation and worldwide. The aim of this study was to explore the effects of plant protein, as part of a plant-based diet, on weight control, body composition, and insulin resistance in overweight individuals. This study is a secondary analysis of data from a 16-week randomized clinical trial. Participants were randomly assigned in a 1:1 ratio to a vegan or a control group. Results indicate that: - the quality and quantity of dietary protein from a plant-based vegan diet are associated with improvements in body composition, body weight, and insulin resistance in overweight individuals. - decreased intake of animal protein and an increased intake of plant protein were associated with a decrease in fat mass. - decreased histidine [amino acid] intake was associated with a decrease in insulin resistance. - decreased intake of the amino acids threonine, leucine, lysine, methionine, and tyrosine were each associated with a decrease in insulin resistance (mainly driven by weight loss). Authors conclude that there is the need for additional research to explore the mechanisms explaining the beneficial role of plant protein and specific amino acids in regulating body weight, body composition, and insulin resistance.
Abstract
BACKGROUND AND OBJECTIVES A plant-based diet is an effective strategy in the treatment of obesity. In this 16-week randomized clinical trial, we tested the effect of a plant-based diet on body composition and insulin resistance. As a part of this trial, we investigated the role of plant protein on these outcomes. SUBJECTS AND METHODS Overweight participants (n = 75) were randomized to follow a plant-based (n = 38) or a control diet (n = 37). Dual X-ray Absorptiometry assessed body composition, Homeostasis Model Assessment (HOMA-IR) assessed insulin resistance, and a linear regression model was used to test the relationship between protein intake, body composition, and insulin resistance. RESULTS The plant-based vegan diet proved to be superior to the control diet in improving body weight, fat mass, and insulin resistance markers. Only the vegan group showed significant reductions in body weight (treatment effect -6.5 [95% CI -8.9 to -4.1] kg; Gxt, p < 0.001), fat mass (treatment effect -4.3 [95% CI -5.4 to -3.2] kg; Gxt, p < 0.001), and HOMA-IR (treatment effect -1.0 [95% CI -1.2 to -0.8]; Gxt, p = 0.004). The decrease in fat mass was associated with an increased intake of plant protein and decreased intake of animal protein (r = -0.30, p = 0.011; and r = +0.39, p = 0.001, respectively). In particular, decreased % leucine intake was associated with a decrease in fat mass (r = +0.40; p < 0.001), in both unadjusted and adjusted models for changes in BMI and energy intake. In addition, decreased % histidine intake was associated with a decrease in insulin resistance (r = +0.38; p = 0.003), also independent of changes in BMI and energy intake. CONCLUSIONS These findings provide evidence that plant protein, as a part of a plant-based diet, and the resulting limitation of leucine and histidine intake are associated with improvements in body composition and reductions in both body weight and insulin resistance.
Methodological quality
Jadad score
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3
Allocation concealment
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Yes
