Changes in ectopic lipids, insulin sensitivity, and beta cell function after a low-fat vegan diet in adults with type 2 diabetes: a 16-week single-arm clinical trial.

Abstract

Objective: The aim of this study was to explore the effects of a low-fat plant-based diet on hepatocellular and intramyocellular lipids, advanced glycation end products (AGEs), insulin resistance, and beta-cell function in adults with type 2 diabetes.

Research design and methods: Participants (n=25) were asked to follow a low-fat vegan diet for 16 weeks. Dual X-ray absorptiometry was used to measure body composition. Hepatocellular and intramyocellular lipids were quantified by ¹H magnetic resonance spectroscopy. Tissue accumulation of AGEs was measured using a skin fluorescence technique. Insulin resistance was assessed in a fasting state with the Homeostasis Model Assessment (HOMA-IR) index. Postprandial insulin sensitivity was assessed with the predicted insulin sensitivity index (PREDIM). Beta-cell function was calculated by a mathematical model after a standard meal, using C-peptide deconvolution.

Results: Mean body weight decreased by 6.0 kg (95% CI -7.0 to -5.1; p<0.001), a 6.6% (95% CI -7.5 to -5.8) decrease relative to baseline. This was largely due to the reduction in fat mass (-4.2 kg, 95% CI -5.7 to -2.7; p<0.001). Visceral fat volume decreased by 290 cm³ (95% CI -467 to -114; p=0.003). Hepatocellular lipids decreased by 33.0% (95% CI -48.7 to -17.3; p<0.001). The AGE score decreased by 0.4 (95% CI -0.6 to -0.2; p=0.002). The HOMA-IR index, a measure of insulin resistance, fell (-2.5, 95% CI -4.1 to -0.9; p=0.004), whereas PREDIM, a measure of insulin sensitivity, increased on the vegan diet (+1.3 mg/min/kg, 95% CI +0.6 to +2.1; p=0.002). Several markers of beta-cell function improved on the vegan diet. Specifically, insulin secretion at 6 and 7 mmol/L glucose, beta-cell glucose sensitivity, rate sensitivity, and potentiation factor all increased.

Conclusions: On an ad libitum low-fat plant-based (vegan) dietary intervention, the participants with type 2 diabetes experienced reductions in ectopic fat, particularly visceral and hepatocellular fat, improvements in insulin sensitivity, reductions in AGEs, and improvements in beta-cell function.

Trial registration number: NCT06106035.