October 14, 2016
2 min read

High-protein weight-loss diets may not improve insulin sensitivity

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In postmenopausal women with obesity, high protein intake during a weight-loss diet may not produce desired improvements in insulin sensitivity typically associated with weight loss, according to findings published in Cell Reports.

“Extra protein intake, therefore, robs [patients] of one of the most desired beneficial effects of weight-loss therapy,” Bettina Mittendorfer, PhD, professor of medicine and nutritional sciences at the Washington University School of Medicine in St. Louis, told Endocrine Today.

Bettina Mittendorfer
Bettina Mittendorfer

Mittendorfer and colleagues evaluated postmenopausal women with obesity randomly assigned to a weight-loss alone group who consumed a hypocaloric diet containing 0.8 g protein/kg body weight per day (n = 10), a high-protein weight-loss group who consumed a hypocaloric diet containing 1.2 g protein/kg body weight per day (n = 10) or a weight-maintenance control group (n = 7).

Participants in the intervention groups were studied before and after 8% to 10% of their baseline body weight was lost and were weight stable for 3 to 4 weeks; the control group was studied after a time-matched weight-maintenance period.

The control group did not exhibit changes in body weight or body composition during the study. Both intervention groups lost about 10% of their initial body weight, but ratio of fat-free mass to total weight loss was about 45% less in the high-protein group compared with the weight-loss alone group (P = .03). Basal insulin concentration decreased by about 30% after weight loss in the intervention groups and was maintained in the control group (P < .05 vs. the control group).

During a hyperinsulinemic-euglycemic clamp procedure, glucose rate of disappearance increased by 25.3% after weight loss in the weight-loss only group (P < .01), whereas the rate did not change in the high-protein group. The weight-loss only group had improvements of 25% to 30% in insulin sensitivity, whereas those in the high-protein group did not. Improvements in insulin sensitivity may translate to a decreased risk for diabetes and cardiovascular disease.

Clinicians should be “promoting a nutritious diet and physical activity with adequate protein for weight maintenance and weight loss to ensure metabolic and muscle health,” Mittendorfer told Endocrine Today. “[There is] no need for extra protein; in fact, too much protein should be discouraged. It does not help lose weight, and while it helps maintain some muscle mass during weight loss, it does not improve function. Weight loss alone improves physical function.” – by Amber Cox

For more information:

Bettin a Mittendorfer, PhD, can be reached at mittendb@wustl.edu.

Disclosure: Mittendorfer reports no relevant financial disclosures.