WASHINGTON, D.C. — Adults with type 2 diabetes who followed a low-fat vegan diet for 16 weeks, eating as much as they wanted, with no calorie counting or portion control, lost weight, reduced fat buildup in the liver and abdomen, and improved insulin sensitivity and beta-cell function, according to a new clinical trial published in BMJ Open Diabetes Research & Care .
The study, led by researchers at the Physicians Committee for Responsible Medicine, in collaboration with the Yale School of Medicine, is the first to simultaneously measure liver fat, muscle fat, visceral fat, and tissue advanced glycation end-products (AGEs) in a single plant-based dietary intervention in people with type 2 diabetes, offering a more complete picture of how diet reverses the underlying mechanisms that drive the disease.
"For years, people with diabetes have been told to count calories and measure portions. This study shows that a simple shift in what you eat—toward vegetables, whole grains, legumes, and fruit—can reduce the fat clogging the liver by a third and improve how the pancreas makes insulin, without anyone having to count a single calorie," said Hana Kahleova, MD, PhD, the lead author of the study and director of clinical research at the Physicians Committee for Responsible Medicine.
Key Findings
- Body weight fell by an average of 6.0 kg (6.6%), driven mainly by loss of fat mass (-4.2 kg); visceral (abdominal) fat volume dropped by 290 cm³.
- Hepatocellular (liver) lipid content, a key driver of insulin resistance, fell by 33%.
- Tissue accumulation of advanced glycation end-products (AGEs), which contribute to insulin resistance and beta-cell damage, decreased significantly.
- Insulin resistance (HOMA-IR) improved, and insulin sensitivity (OGIS and PREDIM) increased.
- Multiple markers of pancreatic beta-cell function improved, including glucose-stimulated insulin secretion, beta-cell glucose sensitivity, rate sensitivity, and potentiation factor.
- HbA1c fell by 1.0 percentage point, and total and LDL cholesterol both decreased significantly.
- These changes occurred without a prescribed calorie target; participants were counseled to eat to satiety on a low-fat, plant-based diet (about 75% of calories from carbohydrates, 15% from protein, and 10% from fat).
"This research adds to a growing body of evidence that food can work like medicine for people with diabetes. When patients don't have to weigh their portions or track every calorie, healthy eating becomes something they can actually sustain, and that is when we see real, lasting metabolic change," said Dr. Kahleova.
Founded in 1985, the Physicians Committee for Responsible Medicine is a nonprofit organization that promotes preventive medicine, conducts clinical research, and encourages higher standards for ethics and effectiveness in education and research.
