High protein diets have become very popular for weight loss. Eating more protein is believed to suppress hunger, as well as prevent loss of lean muscle mass while the body is losing fat. One of the benefits of weight loss is increased insulin sensitivity, an improvement in health that reduces the risk of developing type 2 diabetes.
Yet new research suggests a high protein diet cancels out the improvements in insulin sensitivity, also known as insulin resistance, typically seen with weight loss on a diet with moderate amounts of protein.
Understanding insulin resistance
A consequence of excess body fat is impaired insulin sensitivity. Insulin is a hormone released after eating that allows sugar to leave the bloodstream and enter the body’s individual cells. After years of a sedentary lifestyle fueled by overeating, cells build a tolerance to insulin. The pancreas responds by cranking out more insulin. A vicious cycle ensues. Cells become more insulin resistant as the pancreas wears out from producing so much insulin. Sugar builds up in the blood and type 2 diabetes is the inevitable result.
Losing weight via healthy eating and exercise is a proven way to reduce insulin resistance. However, findings from a recent new study, published in the journal Cell Reports, have shown that individuals adopting a high-protein diet to lose weight may not reap this critical benefit.
Researchers from the Washington University School of Medicine in St Louis recruited 34 postmenopausal women classified as obese with a body mass index of 30 or more who were separated into different treatment groups. One group of women was assigned to maintain their current weight. A second group was placed on a weight loss diet including the recommended daily allowance (RDA) of 0.8 grams of protein per kilogram of body weight. The third group had their protein intake boosted to 1.2 grams per kilogram.
After 28 weeks, among many improvements in their metabolism, researchers documented a 25 to 30 percent decrease in insulin resistance for the women following the RDA for protein intake. According to the researchers, the expected effects of weight loss for the women on the high protein diet were “completely abolished.”
Your protein needs
The study couldn’t answer the question as to why insulin sensitivity did not improve in the high protein diet group. They conceded that further research is necessary. For now, the safety and effectiveness of high protein diets for weight loss remain controversial.
Trying to figure out how much protein you need could get confusing. It’s important to realize that the RDA for protein, 0.8 grams per kilogram, is the absolute minimum the average person needs to avoid protein deficiency. For someone who weighs 140 pounds, that’s 53 grams of protein—212 calories—a day. For the average person on a 2,000-calorie diet, that’s little more than 10 percent of daily calories.
Meanwhile, current Dietary Guidelines for Americans recommend a protein intake of 10 to 35 percent of daily calories, depending on the individual. For our 140-pound person, that’s from 200 to 700 protein calories a day.
More than meat
Until more definitive guidelines on protein intake emerge, if you decide to boost your protein intake to lose weight, don’t just increase your meat intake. Other high quality protein sources low in saturated fat and processed carbohydrates include whole grains, legumes (beans, peas, lentils, peanuts), nuts and certain vegetables. Plus, it’s important to realize that when you increase your calories from protein, you have to decrease calories from carbohydrates and fat or you will defeat your purpose.
Harvard Medical School