Plant-based diet index score is not associated with body composition: A systematic review and meta-analysis

We hypothesized that a plant-based diet, without excluding any specific animal food, may be beneficial for body composition. This study aims to evaluate if the consumption of a plant-based diet affects body composition of adults, through a systematic review of the literature. The review was reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. The literature search was conducted in EMBASE, PubMed, Scopus, and Web of Science in February 2021. Cross-sectionals, interventional trials, and cohort studies were included if changes in the body composition were associated with plant-based index (PDI). Meta-analyses were performed using DerSimonian and Laird random effects model with 95% confidence intervals (CIs) even in the absence of statistical heterogeneity. A total of 6680 citations were found in the systematic search, and after the screening process, 12 studies were included. Of the 11 studies evaluating body mass index, 8 provided data of body mass index (BMI) from a total of 134,128 participants among the quantiles of PDI. A meta-analysis was performed (standardized mean difference [SMD] = 0.17 kg/m²; 95% CI, 0.02-0.32). Of the 7 studies that evaluated waist circumference (WC), 4 provided data of WC among the quantiles of PDI from a total of 12,968 participants. As with BMI, the pooled analysis indicated an increase (SMD = 0.50 kg/m²; 95% CI, 0.01-1.00) of WC as greater was the PDI. Both analyses were influenced by a large study, and in the sensitive analysis the significance was lost. Our findings did not reflect an association between a higher PDI and body composition. Also, most studies evaluating total and central adiposity did not find any association with the PDI. Probably, PDI must be considered in the context of food processing, considering that not all vegetable foods are healthy.