Association between adherence to plant-based dietary patterns and obesity risk: a systematic review of prospective cohort studies

The worldwide prevalence of obesity and its comorbidities is staggering, and elevated body mass index represents a leading risk factor of death globally. Consistent evidence demonstrates a high-quality plant-based diet as an effective intervention for weight management, although it may be particularly challenging to adopt in its entirety for habitual meat consumers or individuals with especially poor-quality diets. Plant-based diets are increasingly studied using indices such as the overall plant-based diet index (PDI), healthful PDI, and unhealthful PM, which offer more flexibility than a binary classification of vegetarianism and better facilitate translation into dietary recommendations. We summarized these recently accumulated studies to comprehensively evaluate plant-based diets in relation to obesity risk. We searched Medline, Embase, and CINAHL databases through January 2022 and identified 9 prospective adult cohorts. Reporting of results was consistent with Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines and certainty of the evidence was assessed using domains from GRADE. The PDI had a protective association with body weight gain and adiposity. Emphasis of healthful plant foods strengthened this association and emphasis of unhealthful plant foods demonstrated either a positive or null association. The certainty of the evidence was considered moderate. These findings have wide application to inform dietary interventions and sustainable policy recommendations.