Vegan diet promotes weight loss and increases insulin sensitivity: JAMA
A recent trial suggests low-fat plant-based dietary intervention reduces body weight by reducing energy intake and increasing postprandial metabolism. The trial details were published in JAMA Network Open on November 30, 2020.
Studies have reported that people following a vegan diet have lower concentrations of intramyocellular lipids compared with those following omnivorous diets, suggesting that by reducing intramyocellular or hepatocellular lipid levels, a plant-based diet may lead to increased mitochondrial activity and postprandial metabolism. This is particularly important because the accumulation of lipids in muscle and liver cells may also be associated with insulin resistance and type 2 diabetes. A research team of Washington DC conducted a randomized controlled, parallel design, single centred trial to measure the effects of a low-fat vegan diet on body weight, insulin resistance, postprandial metabolism, and intramyocellular and hepatocellular lipid levels in overweight adults between January 2017 and February 2019.
A total of 244 adults (87% were female, 48% were white) of mean age 54.4 (11.6) years with a body mass index (BMI) of 28 to 40 were included in the trial and followed for 16 weeks from baseline. The participants were randomized either to the intervention group (n = 122) and were asked to follow a low-fat vegan diet or to the control group (n = 122) with no diet changes for 16 weeks.
Researchers assessed the bodyweight at weeks 0 and 16 using a calibrated scale. They also measure body composition and visceral fat using dual X-Ray absorptiometry and assessed the insulin resistance with the homeostasis model assessment index and the predicted insulin sensitivity index (PREDIM). Thermic effect of food was measured by indirect calorimetry over 3 hours after a standard liquid breakfast (720 kcal). A subset of participants (n = 44) was also evaluated, their hepatocellular and intramyocellular lipids were quantified by proton magnetic resonance spectroscopy.
Key Findings of the study:
♦Over the 16 weeks, researchers observed a decrease in body weight among participants in the intervention group by 5.9 kg
♦They also observed the thermic effect of food was increased in the intervention group by 14.1%.
♦They found the homeostasis model assessment index was decreased by −1.3 and PREDIM increased by 0.9
♦They also found hepatocellular lipid levels were decreased in the intervention group by 34.4%, from a mean of 3.2% to 2.4% and intramyocellular lipid levels were decreased by 10.4%, from a mean of 1.6 to 1.5.
♦None of these changes was observed in the control group for over 16 weeks.
♦The researchers explicated the change in PREDIM correlated negatively with the change in body weight and changes in hepatocellular and intramyocellular lipid levels correlated with changes in insulin resistance
The authors concluded, " A low-fat plant-based dietary intervention reduces body weight by reducing energy intake and increasing postprandial metabolism. The changes are associated with reductions in hepatocellular and intramyocellular fat and increased insulin sensitivity".
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