A plant-based diet in overweight adults in a 16-week randomized clinical trial: The role of dietary acid load

Abstract

Background: Evidence suggests that changes in dietary acid load may influence body weight, body composition, and insulin sensitivity.

Methods: Participants (n = 244) were randomly assigned to an intervention (vegan) (n = 122) or control group (n = 122) for 16 weeks. Before and after the intervention period, body composition was measured by dual X-ray absorptiometry. Insulin resistance was assessed with the Homeostasis Model Assessment (HOMA-IR) index and predicted insulin sensitivity index (PREDIM). Repeated measure ANOVA was used for statistical analysis.

Results: Potential Renal Acid Load (PRAL) and Net Endogenous Acid Production (NEAP) decreased significantly in the vegan group with no change in the control group (treatment effect -24.7 mEq/day [95% CI -30.2 to -19.2]; p < 0.001; and -23.8 mEq/day [95% CI -29.6 to -18.0]; p < 0.001, respectively). Body weight decreased by 6.4 kg in the vegan group, compared with 0.5 kg in the control group (treatment effect -5.9 kg [95% CI -6.8 to -5.0]; Gxt, p < 0.001), largely due to a reduction in fat mass and visceral fat. HOMA-IR index decreased and PREDIM increased in the vegan group. After adjustment for energy intake, changes in PRAL and NEAP correlated positively with changes in body weight (r = +0.37; p < 0.001; and r = +0.37; p < 0.001, respectively), fat mass (r = +0.32; p < 0.001; and r = +0.32; p < 0.001, respectively), visceral fat (r = +0.19; p = 0.006; and r = +0.15; p = 0.03, respectively), and HOMA (r = +0.17; p = 0.02; and r = +0.20; p = 0.006, respectively), and negatively with changes in PREDIM (r = -0.22; p = 0.002; and r = -0.27; p < 0.001, respectively).

Conclusion: Dietary acid load as part of a plant-based diet was associated with changes in body weight, body composition, and insulin sensitivity, independent of energy intake. Mechanistic explanations suggest that the relationship may be causal.

Trial registration: ClinicalTrials.gov number, NCT03698955.

Keywords: Diet; Dietary acid load; Nutrition; Vegan; Weight.

Conflict of interest statement

Declaration of competing interest All authors except for AT and RH work or have worked for the Physicians Committee for Responsible Medicine in Washington, DC, a nonprofit organization providing educational, research, and medical services related to nutrition. Dr. Barnard is an Adjunct Professor of Medicine at the George Washington University School of Medicine. He serves without compensation as President of the Physicians Committee for Responsible Medicine and the Barnard Medical Center in Washington, DC. He writes books and articles and gives lectures related to nutrition and health and has received royalties and honoraria from these sources.

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