Eating less protein may slow aging and extend lifespan – Earth.com
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08-01-2026
Too much protein may be aging your body faster, scientists warn
BySanjana Gajbhiye
Earth.com staff writer
Americans are being told to eat more protein than ever before. Food companies have responded by adding it to everything from cereal and coffee to bottled water
But a review of more than 350 studies suggests most people may benefit from eating less protein, not more
The results of the analysis indicate that eating less protein can improve health and and even help some people live longer
Protein is everywhere now
Health officials recently raised the protein target to 0.5 to 0.7 grams per pound of body weight. That is nearly double the older allowance of 0.4 grams per pound
Food makers have followed the trend and packed protein into more products
In 2024, 61 percent of American shoppers said they were eating more of it, up from 48 percent five years earlier
Bailey Knopf and Dudley Lamming reviewed more than 350 papers on protein restriction and aging. Most of those papers tested animals, not people
Flies, worms, and rodents show the strongest lifespan results. In those animals, low-protein diets often improved metabolism and extended life
Less protein may help aging
Animals that eat fewer calories tend to live longer, across many species. The same diets also lower the risk of age-related illness, including some cancers
The problem is that most people cannot stick to a low-calorie diet. A low-protein diet produces some of the same benefits even when calories stay the same
“It’s absolutely crystal clear that there are benefits of protein to muscle growth and exercise response of active individuals,” said Dudley Lamming, the paper’s corresponding author, of the University of Wisconsin-Madison
“But because most people are relatively sedentary, many people are likely consuming more protein than they actually need, which probably has negative health consequences.”
Short human trials show the same pattern. People who cut their protein lost weight and fat and improved their blood sugar, even while eating more calories
One hormone helps explain why. It is called FGF21, and it rises when protein runs low
The hormone raises energy use, improves blood sugar control, and lowers inflammation. Mice engineered to make extra FGF21 lived longer, about 30 percent longer in males and 40 percent in females
“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
What happens in cells
A low-protein diet does more than shift weight. It changes how cells respond to the food coming in
Less protein lowers the activity of the body’s main growth sensor. That sensor stays highly active on protein-rich diets
Cells then do more of their own cleanup, clearing out damaged parts. The cleanup keeps tissues working well for longer and cuts the buildup of worn-out cells that cause inflammation
The benefits appear even when the diet starts late in life. Older mice moved onto less protein still improved
Which amino acids matter
Protein is built from amino acids. A few of them seem to drive these effects
The three that stand out are methionine, isoleucine, and valine. In large amounts, these amino acids switch on growth signals linked to obesity, inflammation, and other age-related disease
Methionine restriction on its own extends the lifespan of rodents. The amino acid is common in meat, eggs, and fish
Isoleucine and valine belong to the branched-chain amino acids that many people take as supplements. Cutting either one in mice improved their metabolism. Both also extended life in male animals
Plant protein may support healthier aging
Thedo not act the same way
Plant protein has been tied to a lower risk of frailty. Animal protein has not shown the same link
People on Okinawa are a long-studied example. Their traditional diet is about nine percent protein, most of it from plants, and they have long been known for healthy old age
They also eat fewer calories overall. So the low protein is only part of the story
Exercise changes the picture
The picture is not one-sided. Some studies show that more protein, paired with exercise, helps older adults keep their muscle
That finding is part of why the guidelines went up. Muscle loss with age is a serious problem, and protein plainly helps active people build muscle back
Athletes are the real puzzle here. They eat large amounts of protein and rarely get metabolic disease
Lamming suspects that exercise protects them, by using the protein to build strong, healthy muscle. Regular movement may cancel out the harm that a protein-rich diet can cause in people who barely move
Personalize the advice
“Recent recommendations have encouraged people to eat more protein, but they’ve also encouraged people to exercise more,” Lamming said
“We probably need to personalize protein recommendations based not just on age, but also on how physically active people are.”
Some people genuinely need more protein, not less. That group includes pregnant women, growing children, some older adults, and people healing from injury
For those groups, a low-protein plan could backfire. They are building or repairing tissue, and that work needs protein
What is still unknown
No one knows yet how eating less protein affects human lifespan. Most of the lifespan data still come from animals
This work reviews past findings rather than running a fresh experiment. It points to what researchers should test next in people
Many older adults already eat too little protein, from poor appetite or a tight budget. For them, cutting back could do real harm
The study is published in the journalCell Press Blue
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