Participants who followed the plant-based diet for the 16-week intervention period saw increases in meal-stimulated insulin secretion and pancreatic beta-cell glucose sensitivity, found the research team led by the from the Physicians Committee for Responsible Medicine.
Compared with controls, the plant-based diet group also had lower fasting insulin resistance and decreased fasting and postprandial blood glucose levels.
The intervention group followed a low-fat vegan diet based on fruits, vegetables, whole grains and legumes with unlimited calorie intake. The macronutrient composition of the diet was around 75% energy from carbohydrates, 15% from protein and 10% from fat. The control group continued to consume their regular diet.
“In conclusion, we have demonstrated that beta-cell function and fasting insulin sensitivity can be modified by a 16-week dietary intervention. Our study suggests the potential of a low-fat plant-based diet in diabetes prevention, addressing both core pathophysiologic mechanisms—insulin resistance and diminished beta-cell function—at the same time,” wrote lead author Dr. Hana Kahleova.
The study findings are important in the context of the obesity epidemic facing many Western countries.
"The study has important implications for diabetes prevention," commented Kahleova."Type 2 diabetes affects approximately 30 million Americans, with 84 million more suffering from prediabetes.
"If nothing changes, our next generation--the first expected to live shorter lives than their parents--is in trouble. A third of young Americans are projected to develop diabetes in their lifetimes," she continued.
"Fortunately, this study adds to the growing evidence that food really is medicine and that eating a healthful plant-based diet can go a long way in preventing diabetes."
The plant-based diet consumers also experienced significant reductions in ‘bad’ low-density lipoprotein (LDL) cholesterol, body mass index (BMI), fat-mass and importantly, visceral fat volume.
Visceral fat is widely recognised as being linked with insulin resistance, fatty liver and type-2 diabetes. Previous research has also suggested that metabolic crosstalk of fatty liver with pancreatic beta-cell islets may contribute to an obesity-related decrease in beta-cell glucose tolerance.
The researchers emphasised that the decrease in insulin resistance displayed in the study was primarily liver-related (hepatic insulin resistance) rather than in peripheral tissues. This was reflected by the observed decrease in Homeostasis Model Assessment (HOMA-IR) together with unchanged postprandial oral glucose insulin sensitivity.
All but one of the 38 intervention group (and all but two of the control group) participants completed the trial. (The exceptions withdrew for non-diet related reasons). The researchers therefore advocated that the diet was both acceptable and sustainable. They also highlighted the advantage that the study was conducted in a free-living environment.
“Our participants were generally health-conscious individuals who were willing to make substantial changes to their diet,”
“Given that the participants were living at home and preparing their own meals or eating at restaurants, our results are applicable outside the research setting, in free-living conditions.”
This might assist others seeking help for weight problems, the researchers concluded.
Volume 10, issue 2, Article 189, doi: 10.3390/nu10020189
“A Plant-Based Dietary Intervention Improves Beta-Cell Function and Insulin Resistance in Overweight Adults: A 16-Week Randomized Clinical Trial”
Authors: Hana Kahleova, Andrea Tura, Martin Hill, Richard Holubkov and Neal D. Barnard