Background: The aim of this study was to test the effect of a 16-week plant-based dietary intervention on beta-cell function and insulin resistance in overweight adults with no history of diabetes.

Methods: Participants (n=75) were randomized to follow a low-fat vegan diet (n=38) or to make no diet changes (n=37) for 16 weeks. At baseline and 16 weeks, beta-cell function was assessed during standard meal tests. Insulin secretory rate was calculated by C-peptide deconvolution, and beta-cell function was quantified with a mathematical model. HOMA-IR (The Homeostasis Model Assessment) index was used to assess insulin resistance while fasting. Repeated measure ANOVA was used for statistical analysis.

Results: A marked increase in glucose-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.

Conclusions: A 16-week low-fat vegan dietary intervention improved beta-cell function and insulin resistance in overweight adults. The improvement in insulin resistance was related to loss of visceral fat, independent of changes in BMI.


H. Kahleova: None. A. Tura: None. M. Hill: None. R. Holubkov: Other Relationship; Self; Pfizer Inc., MedImmune. N. Barnard: None.

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