Could a High-Protein Diet Nullify Weight-Loss Benefits?

New research finds that maintaining a diet that is high in protein can reverse improvements in insulin sensitivity associated with weight loss, which in turn could affect diabetes risk.

For their study, Washington University School of Medicine investigators examined 34 postmenopausal women between the ages of 50 and 65. While all participants had body mass indices of at least 30 (indicating obesity), none had diabetes. For the 28-week study, patients were randomly assigned to 1 of 3 groups. A control group was asked to maintain their weight, while the second group adhered to a weight-loss diet that included consuming 0.8 grams per kilogram of body weight of protein, the recommended daily allowance (RDA) of protein. The third group ate a diet geared toward weight loss, but also consumed 1.2 grams per kilogram of body weight of protein.
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Women in the group that consumed the recommended daily amount of proteins saw the biggest benefits to their metabolism, according to the authors. Most notably, participants from this group saw a 25% to 30% improvement in their insulin sensitivity, which the authors note lowers the risk of diabetes and cardiovascular disease. The women adhering to a high-protein diet, however, did not experience the same type of improvements.

"Obesity is a well-known risk factor for insulin resistance, which in turn increases the risk of developing type 2 diabetes," said Gordon Smith, PhD, an assistant professor of medicine in the Center for Human Nutrition, Division of Geriatrics and Nutritional Sciences at Washington University School of Medicine, and a co-author of the study.

"Weight loss through calorie restriction is frequently prescribed to improve metabolic health, and we observed this to be the case in individuals consuming a diet containing the recommended intake of protein per day," continued Smith.

In contrast, no improvement in insulin resistance and several other markers of metabolic health was observed in individuals that consumed a high protein diet containing 50% more protein per day than currently recommended, he said.

"Based on these data, primary care practitioners should caution against recommending high protein diets in patients wanting to lose weight, especially those with preexisting insulin resistance," added Smith, who recommends that primary care physicians instead encourage patients to "focus on consuming a nutritious diet containing the RDA of protein in conjunction with a supervised increase in physical activity, [which] would seem prudent to improve overall metabolic and muscle health."

—Mark McGraw  

Reference:

Smith GI, Yoshino J, Kelly SC, et al. High-protein intake during weight loss therapy eliminates the weight-loss induced improvement in insulin action in obese post-menopausal women [published online October 11, 2016]. Cell Reports. doi:http://dx.doi.org/10.1016/j.celrep.2016.09.047.