A study in mice shows that progressive resistance strength training can reduce the negative effects of a high-protein diet on metabolism. The study found that sedentary mice fed a high-protein diet accumulated more fat, while mice that received resistance training gained muscle and accumulated less fat. However, their glycemic control is still adversely affected by high protein intake. This study highlights the importance of resistance training for people eating high-protein diets, especially those who live a sedentary life.
Researchers reveal a paradox: While high-protein diets improve athletic performance, they can also lead to health problems and shortened lifespans in non-athletes.
Resistance strength training may counteract the adverse effects of a high-protein diet, according to new research in mice.
The study, recently published in the journal eLife, is considered by the editors to be a valuable finding on the relationship between a high-protein diet and resistance exercise on fat accumulation and glucose homeostasis, supported by solid evidence. They say the findings are of interest to nutritionists and others trying to understand the link between dietary protein, diabetes and exercise.
Dietary protein: benefits and risks
Dietary protein provides essential nutrients, controls various processes in the body, and can influence health and longevity. It is generally accepted that protein intake is beneficial for promoting muscle growth and strength, especially when combined with exercise. However, for sedentary people, consuming too much protein can increase the risk of heart disease, diabetes, and death.
"We know that low-protein diets and diets that reduce the content of certain amino acids promote health and longevity in animals, and that short-term protein restriction can improve health in metabolically unhealthy adults," explained lead author Michaela Trautman, a research associate in the Department of Medicine at the University of Wisconsin School of Medicine and Public Health. "But this creates a paradox - if high protein in the diet is so harmful, then many people who take high-protein meals or protein supplements will be overweight and have an increased risk of diabetes, while athletes who take high-protein meals are among the most metabolically healthy people."
Experiment overview
To study whether exercise could protect against the harmful effects of a high-protein diet, researchers used a progressive resistance strength training program in mice. For three months, the mice walked along a track three times a week pulling a cart with increasing loads, or pulled a cart without any load for the same period of time.
The team fed one group of mice a low-protein diet (7% of calories from protein) and another group of mice a high-protein diet (36% of calories from protein). The team then compared the different groups' body composition, weight and metabolic measures such as blood sugar.
The results were as the team expected: The high-protein diet harmed the metabolic health of sedentary mice; these mice gained excess fat compared with mice on the low-protein diet. But in mice that gained weight, a high-protein diet promoted muscle growth, especially in the forearms, and protected the animals from gaining weight. However, exercise did not protect mice from the effects of high protein on glycemic control.
Additionally, while mice fed a high-protein diet gained strength faster than mice fed a low-protein diet, there was no difference in the maximum weight each group could pull at the end of the study period, even though the mice fed the high-protein diet were larger and more muscular.
While the evidence supporting the study is considered reliable, the editors highlight several limitations. For example, the use of mice may limit the generalizability of findings to humans due to inherent differences in physiology. The editors note that the findings would be further strengthened by direct investigation of the underlying molecular mechanisms responsible for the observed results.
"We know that despite overwhelming evidence that high protein levels can adversely affect metabolism, many people who intentionally consume a high-protein diet or take protein supplements to support exercise regimens," said senior author Dudley Lamming, associate professor in the Department of Medicine (Endocrinology) at the UW School of Medicine and Public Health. People are not metabolically unhealthy. Our study could shed light on this dilemma, as it shows that resistance exercise protects mice from high-protein-induced fat gain, suggesting that people with unhealthy metabolisms, sedentary diets, or protein supplements may benefit from reduced protein intake or increased resistance exercise."