In a 16-week trial of 25 adults, a low-fat vegan diet was linked to lower blood sugar, liver fat and body weight. Larger studies are needed.
A 16-week study in 25 adults with type 2 diabetes found that an all-you-can-eat, low-fat vegan diet was associated with better blood sugar measures and less fat in the liver. Participants also lost weight, even though they weren’t asked to count calories. The results are promising, but this small study can’t show that the diet alone caused the changes or whether they will last.
What the study tested
Researchers from the Physicians Committee for Responsible Medicine and Yale School of Medicine studied a diet built around vegetables, grains, legumes and fruit. It excluded animal products and added fats, with a planned balance of about 75% of calories from carbohydrates, 15% from protein and 10% from fat. Participants were told to eat until satisfied and keep their usual exercise habits.
The study was a single-arm clinical trial: everyone received the same dietary intervention, and there was no comparison group following a different diet. Twenty-five adults began the study and 24 completed it. Their average age was 59, average body mass index was about 31, and they had lived with diabetes for an average of 6.6 years. People taking insulin, sulfonylureas or weight-loss medication weren’t included. Some participants used metformin.
This design can show how participants’ measurements changed over time, but it can’t establish that the diet was responsible for every change. A larger trial with a comparison group would help clarify how the results compare with other eating approaches and how well they apply to people with different health histories.
Changes in weight and body fat
Participants reported eating about 346 fewer calories per day, despite having no calorie limit. Their fiber intake nearly doubled, while total fat intake fell to less than a third of its previous level and saturated fat intake fell to less than a fifth. Protein intake decreased slightly, from about 70 grams to 59 grams per day. Carbohydrate intake rose from 198 to 259 grams per day.
On average, participants lost 6 kilograms, or 6.6% of their starting weight. Their fat mass fell by 4.2 kilograms. The measured volume of visceral fat, which collects around internal organs, decreased by about 290 cubic centimeters, from 2,168 to 1,878. Liver fat fell by an average of 33%.
Some lean mass was lost along with fat. That matters when interpreting weight change: the study didn’t show that all the weight lost came from body fat. Future research could examine how this eating pattern affects lean mass and whether adjustments to the diet change that outcome.
Participants didn’t report increasing physical activity; reported activity actually decreased. The study also found no significant change in energy expenditure while fasting or after meals. Those findings make increased exercise or a measurable rise in energy use less likely explanations for the observed weight loss, though they don’t establish exactly why participants ate less.
Blood sugar, cholesterol and insulin response
Average fasting blood glucose fell from 155 to 116 mg/dL, while HbA1c, a measure of blood sugar over time, dropped from 7.6% to 6.6%. Fasting insulin also decreased, from 13.5 to 8.8 microunits per milliliter. The average HbA1c result ended below 7%, a commonly used treatment goal for many adults with diabetes, though an appropriate goal varies by person.
Researchers also estimated that the insulin-producing beta cells in the pancreas responded more effectively to rising glucose during the study. These measures offer clues about how the body handled blood sugar; they don’t show that diabetes went away or that participants no longer needed ongoing care.
Average LDL cholesterol fell from 108 to 86 mg/dL. HDL cholesterol also decreased, from about 55 to 47 mg/dL, while triglycerides didn’t change significantly. These results show why individual measurements need context: a change in one cholesterol measure doesn’t, by itself, describe a person’s overall heart or metabolic health.
Among the 16 participants using metformin who completed the study, five reduced their dose and two stopped taking it. No participant began a glucose-lowering medicine or increased a dose. These medication changes happened within the study and shouldn’t be taken as evidence that people can alter treatment on their own. Anyone considering a major change in eating habits, or noticing a change in blood sugar, can discuss it with a doctor or pharmacist.
A preliminary finding on skin markers
The researchers measured skin levels of advanced glycation end products, or AGEs. These compounds form when sugars react with proteins or fats, and they can accumulate in body tissues. The average skin AGE score declined from 3.1 to 2.7. This is an early finding from a study designed to measure several types of fat and tissue markers together. It doesn’t establish that the change improves symptoms or prevents complications.
The central takeaway is that this dietary approach was linked to changes in blood sugar, weight and liver fat over 16 weeks, without calorie counting. The small number of participants, lack of a comparison group and short follow-up limit what can be concluded. Larger, longer studies will be needed to test whether the results hold over time and for whom the approach is suitable.
Research cited
[1] Kahleova, H., Petersen, K., Shulman, G. I., Znayenko-Miller, T., Dufour, S., Brennan, H., … & Barnard, N. D. (2026). 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. BMJ Open Diabetes Research & Care, 14(5).
[2] Chang-Chen, K. J., Mullur, R., & Bernal-Mizrachi, E. (2008). β-cell failure as a complication of diabetes. Reviews in Endocrine and Metabolic Disorders, 9(4), 329–343.
[3] Semba, R. D., Nicklett, E. J., & Ferrucci, L. (2010). Does accumulation of advanced glycation end products contribute to the aging phenotype?. Journals of Gerontology Series A: Biomedical Sciences and Medical Sciences, 65(9), 963–975.
