Researchers say weight loss is good, but too much protein can negate some of the effects.
For those who are at risk of developing type 2 diabetes, the advice is consistent: lose weight.
That makes the results of a study that came out earlier this week in the journal Cell Reports pretty startling.
According to the authors, weight loss from a high-protein diet does not improve the body’s sensitivity to insulin (a key factor in staving off diabetes) the way a conventional diet does.
In fact, high-protein dieters in the study saw no improvement in insulin sensitivity at all, while the conventional dieters improved by as much as 30 percent.
Usually, “weight loss has a tremendous benefit,” Dr. Bettina Mittendorfer, a professor at Washington University School of Medicine, and senior author of the paper, told Healthline. “With just a little bit of extra protein you’ve gotten rid of one of the major benefits of weight loss.”
The study focused on postmenopausal women, who are often told to try high protein diets in order to reduce muscle loss.
Women at that age are at a particularly high risk of sarcopenia, a condition in which muscle mass is lost over time.
So Mittendorfer’s team conducted a randomized controlled trial that singled out the effects of extra protein when all other factors remained the same.
They divided a group of 34 women (27 completed the study) between the ages of 50 and 65 into three groups.
One followed a calorie-restricted diet with the recommended daily protein allowance.
Another cut calories but supplemented with whey protein shakes.
And a control group did not diet.
Both the high protein and the conventional dieters lost about 10 percent of their body weight, which would have put them ahead of the Centers for Disease Control (CDC) recommendation that overweight people with prediabetes lose 7 percent of their weight.
Yet, the benefits of weight loss in terms of improved insulin performance were blunted in the high-protein group. They did, however, retain more muscle than conventional dieters, but only by about pound.
Other scientists Healthline contacted said they respected the study design but questioned its relevance to the general population.
“When people eat, especially when they eat a high-protein diet,” they don’t typically eat whey protein isolated, said Marina Chaparro, a diabetes educator at Joe DiMaggio Children’s Hospital in Florida. “They tend to eat a little bit of everything.”
“So yeah it’s a high-protein diet but what type of protein are you choosing?” she added. “In the real world what does this mean?”
People can get their protein from meat, fish, eggs, dairy products, beans, nuts, and seeds. But not all protein is equal.
Diets high in animal-derived protein have been associated with increased diabetes risk when compared with diets high in plant-derived protein. Real foods are bundles of nutrients, vitamins, and fiber.
The researchers also looked at a specific population: postmenopausal women who were at risk for developing diabetes but did not have the disease.
As women lose muscle after menopause, their metabolism changes, Angela Ginn-Meadow, a registered dietician at the University of Maryland Center for Diabetes and Endocrinology, told Healthline.
Metabolically speaking, their situation is unique, she said.
Plus, the researchers did not include exercise as a factor.
Exercise is a natural insulin sensitizer, Ginn-Meadow said. In addition to losing 7 percent body weight, the CDC recommends at least 150 minutes of exercise a week.
The experts say, however, that these caveats just mean the results are worth exploring further.
“I think we’re constantly looking for the remedy for people to lose weight and increase their insulin sensitivity to prevent type 2 diabetes,” Ginn-Meadow said.
At one time, that recommendation was to reduce carb intake to as low as 2 percent of the daily diet, according to the Joslin Diabetes Center.
Now, dietary guidelines for managing diabetes are more flexible.
“The important message is that with proper education and within the context of healthy eating, a person with diabetes can eat anything a person without diabetes eats,” Amy Campbell, a Joslin nutritionist, told a blogger.
As for people who don’t have diabetes but are worried about their risk, Mittendorfer recommends “coming back to the good old things.”
You guessed it: whole foods, balanced meals, and exercise.