Insulin sensitivity does not improve in women who lose weight eating a high-protein diet, according to a small new study from the Washington University School of Medicine in St. Louis.
Insulin sensitivity (how efficiently the body uses insulin to lower blood sugar levels) is important for reducing the risk of Type 2 diabetes, and is a metabolic marker that typically improves when a person loses weight. Since protein increases satiety (feelings of fullness) and is commonly believed to prevent against the loss of muscle, high-protein diets are often recommended for weight loss.
To determine the effects of a high-protein weight-loss diet, researchers worked with 34 postmenopausal women 50–65 years of age with obesity but without diabetes. The participants were randomly assigned to either maintain their body weight, to stick to a weight-loss diet including the recommended daily allowance (RDA) of protein (0.8 grams per kilogram of body weight, or roughly 65 grams of protein daily for a 55-year-old woman weighing 180 pounds), or to stick to a high-protein weight-loss diet (1.2 grams of protein per kilogram of body weight, or approximately 100 grams daily for a 55-year-old woman weighing 180 pounds). For the course of the 28-week study, the investigators provided all of the participants’ meals, which differed in the two weight-loss groups only in the amount of protein, with “very minimal changes in the amount of fat or carbohydrates.”
By the end of the study period, both groups of participants following the weight-loss diets had lost about 10% of their body weight. The women following the weight-loss diet with the recommended amount of protein had also experienced a 25% to 30% improvement in their insulin sensitivity, lowering their risk for Type 2 diabetes and heart disease. However, although they lost on average the same amount of weight, those on the high-protein weight-loss diet did not experience the improvements in insulin sensitivity.
“It’s not that the metabolic benefits of weight loss were diminished — they were completely abolished in women who consumed high-protein diets, even though they lost the same, substantial amounts of weight as women who ate the diet that was lower in protein,” noted principal investigator Bettina Mittendorfer, PhD. “We found that women who lost weight eating a high-protein diet didn’t experience any improvements in insulin sensitivity. However, women who lost weight while eating less protein were significantly more sensitive to insulin at the conclusion of the study. That’s important because in many overweight and obese people, insulin does not effectively control blood sugar levels, and eventually the result is Type 2 diabetes.”
The scientists plan to do further research to investigate why insulin sensitivity was not improved in women on the high-protein diet and whether men or women already diagnosed with Type 2 diabetes would experience the same outcome.
For more information, see the article “High-Protein Diet Curbs Metabolic Benefits of Weight Loss” or the study’s abstract in the journal Cell Reports. And to learn more about approaches to weight loss that work, read “Tried and True Weight-Loss Techniques.”
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