Consuming less protein, especially among those who are relatively sedentary, could have greater health benefits and may extend lifespan, according to a new review.
“It’s absolutely crystal clear that there are benefits of protein to muscle growth and exercise response of active individuals,” author Dudley Lamming, of the University of Wisconsin-Madison in the US, said.
“But because most people are relatively sedentary, many people are likely consuming more protein than they actually need, which probably has negative health consequences,” Lamming said.
The study, published in the journal Cell Press Blue, reviewed 350 papers on protein restriction and aging.
Previous studies have found that eating less protein can extend the lifespan of flies and rodents without reducing calorie consumption.
Researchers added that several recent clinical trials in humans have also shown that reducing protein intake can reduce weight and fat mass and improve fasting blood sugar in humans, even though protein-restricted individuals tend to eat more calories.
However, when paired with exercise, consuming more protein has been shown to promote weight loss and reduce age-related muscle loss in older adults.
The researchers outlined potential mechanisms that consistently emerge across studies, which may explain how protein-restricted diets could improve health and promote longevity. The mechanisms suggest that protein restriction slows aging by improving metabolism, changing how cells respond to nutrients, reducing cellular damage, and preserving healthy cell function.
The hormone ‘fibroblast growth factor 21 (FGF21)’ was found to be a key player. Levels of the hormone increase when protein intake is low. FGF21 can increase the body’s energy expenditure, improve blood sugar control and reduce inflammation.
Studies in mice have shown that animals with higher FGF21 levels lived longer than normal mice, and the benefit was more pronounced in male mice than female mice. Eating less protein raises FGF21 levels in humans as well, the researchers said.
The review also highlighted amino acids — the building blocks of protein — that appear to drive many of the ageing effects, including methionine, isoleucine and valine.
Studies show that consuming too much of these amino acids could trigger biological processes that promote growth, increasing the risk of obesity, inflammation and other age-related diseases.
“These studies show that the amount of protein sedentary people are eating today may have negative health consequences, at least at the population level,” Lamming said.
He added that while pregnant women and older adults may have higher protein needs, for most sedentary adults, protein-fortified food may not provide the health benefits people expect.
“Overall, this review provides a comprehensive overview of current knowledge regarding the benefits of PR (protein restriction) and amino acid restriction for healthy aging and highlights the therapeutic potential of interventions based on these diets to promote healthspan and longevity,” they wrote.
Published on August 3, 2026
