Vegetarian diet trims thigh fat related to insulin resistance
Type 2 diabetes (T2D) patients following a plant-based diet shed more fat in the thighs compared with those consuming a conventional hypocaloric diabetic diet, with subfascial and intramuscular fat reductions associated with improvements in glucose and lipid metabolism, according to a study presented at the 77th Scientific Sessions of the American Diabetes Association (ADA) 2017 in California, US.
"Losing muscle fat increases insulin sensitivity," said principal investigator Dr Hana Kahleova, director of clinical research at the nonprofit Physicians Committee, in a news release. "By taking extra fat out of the muscle cells, we're letting insulin back in to convert sugar into energy. This uptick in the conversion of calories is the equivalent to a metabolic reboot, especially for people who struggle with extra weight, a sluggish metabolism, or T2D."
Kahleova and colleagues equally randomized 74 T2D patients to follow either a vegetarian diet (eg, cooked millet with plums and almonds, lentil soup with carrots and cabbage) or an isocaloric conventional antidiabetic diet (control; eg, peanut butter raisin oatmeal, tuna-cucumber wrap) for 6 months. Both diets were calorie restricted (−500 kcal/day), and the diets were combined with aerobic exercise from week 13 to 26.
Compared with the control group, the vegetarian group showed a greater reduction in total leg area (−13.6 vs −9.9 cm2; p<0.001). Reductions in subfascial and intramuscular fat were particularly greater in response to a plant-based diet (−0.82 vs −0.44 cm2; p=0.04 and −1.78 vs −0.57 cm2; p=0.12), whereas the decrease in subcutaneous fat was comparable in response to both diets (p=0.64). [ADA 2017, abstract 780]
Subcutaneous and subfascial fat reductions correlated with changes in glycated haemoglobin (p<0.05), fasting plasma glucose (p<0.01) metabolic clearance rate of glucose (p<0.05), resting energy expenditure (p<0.05) and β-cell insulin sensitivity (p<0.05). Correlations for changes in fasting plasma glucose, β-cell insulin sensitivity and triglycerides persisted despite adjustment for changes in body mass index.
“These results are in accordance with previous research … demonstrating that subfascial and intramuscular fat are markers of insulin resistance in obesity and T2D, suggesting that a decrease in subfascial and intramuscular fat is associated with improvements in insulin resistance,” Kahleova noted. [Am J Clin Nutr 2000;71:885–892]
“It appears that there is a regional pattern of thigh adipose tissue distribution, specifically an increased subfascial fat in patients with T2D, that is associated with insulin resistance. It seems that reduction in fat content in this specific metabolically adverse depot may have a beneficial effect on glucose metabolism,” she added.
A tool for staying healthy and lean
Aside from the reductions in muscle fat, the vegetarian diet also provided additional benefits such as satiety and increased energy during the 3- and 6-month follow-up. Adherence to both the diet and exercise was also higher in the vegetarian vs the control group (55 vs 32 percent and 90.3 vs 80.6 percent).
“What we found is that a plant-based vegetarian diet is a helpful tool for anyone who is serious about staying healthy and lean, especially as we age,” Kahleova said. “A diet built around plants is naturally rich in fibre, vitamins, minerals and phytochemicals, which leaves us feeling energized and refreshed instead of hungry and fatigued. Part of the reason a vegetarian diet works so well for many people is because it's easy to stick to.”
She also pointed out the importance of exercise in weight-loss programmes in preserving lean mass. Given that thigh muscle mass has been shown to be protective against the risk of diabetes and coronary heart disease, exercise helps prevent muscle loss during a dietary intervention, which factors in reducing cardiometabolic risk. [Obesity (Silver Spring) 2014;22:2071–2079; J Nutr Metab 2011:676208]
“Further research is needed to determine how dietary interventions with different diet composition can influence thigh fat distribution in relationship to glucose and lipid metabolism,” she added.