The aim of this study was to test the effect of a plant-based dietary intervention on beta-cell function in overweight adults with no history of diabetes. Participants (n = 75) were randomized to follow a low-fat plant-based diet (n = 38) or to make no diet changes (n = 37) for 16 weeks. At baseline and 16 weeks, beta-cell function was quantified with a mathematical model. Using a standard meal test, insulin secretory rate was calculated by C-peptide deconvolution. The Homeostasis Model Assessment (HOMA-IR) index was used to assess insulin resistance while fasting. A marked increase in meal-stimulated insulin secretion was observed in the intervention group compared with controls (interaction between group and time, Gxt, p < 0.001). HOMA-IR index fell significantly (p < 0.001) in the intervention group (treatment effect -1.0 (95% CI, -1.2 to -0.8); Gxt, p = 0.004). Changes in HOMA-IR correlated positively with changes in body mass index (BMI) and visceral fat volume (r = 0.34; p = 0.009 and r = 0.42; p = 0.001, respectively). The latter remained significant after adjustment for changes in BMI (r = 0.41; p = 0.002). Changes in glucose-induced insulin secretion correlated negatively with BMI changes (r = -0.25; p = 0.04), but not with changes in visceral fat. Beta-cell function and insulin sensitivity were significantly improved through a low-fat plant-based diet in overweight adults.

Institute of Endocrinology 11394 Prague Czech Republic

Metabolic Unit CNR Institute of Neuroscience 35127 Padua Italy

Physicians Committee for Responsible Medicine Washington DC 20016 USA

Physicians Committee for Responsible Medicine Washington DC 20016 USA Adjunct Faculty George Washington University School of Medicine and Health Sciences Washington DC 20016 USA

School of Medicine University of Utah Salt Lake City UT 84132 USA

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