The curious case of low-protein diets | Knowable Magazine

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While it’s not a recommended choice for people, a restricted protein diet prolongs life in lab animals.

Living World<br>The curious case of low-protein diets<br>In the lab, animals live longer on less of the stuff. How could this be, and what does it mean for human aging?<br>By Amber Dance 02.19.2026<br>Facebook<br>Bluesky<br>Twitter<br>LinkedIn<br>WhatsApp<br>Reddit<br>Flipboard<br>Email<br>Print<br>Republish

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Lea en español<br>Protein dominates the grocery shelves: Protein chips. Protein cookies. Protein water. It’s in the headlines, too: January’s new US dietary guidelines raised the recommended amount from 0.8 grams of protein per kilogram body weight to 1.2 to 1.6 grams.<br>Yet there’s a cadre of scientists studying a contrary phenomenon: In critters from single-celled yeast to insects to rodents, cutting protein intake to measly levels makes them live longer.<br>YOU MAY ALSO LIKE

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Could it work for people? To be clear: The body needs protein to build and repair its parts, and a diet with about 7 percent or less of its calories from protein is a recipe for malnutrition, not centenarian status. But studying protein restriction in lab animals helps scientists learn how animals sense nutrients, how their bodies strategically respond to excess or to shortage, and how all of this affects their health and longevity. And that could carry lessons for human beings.<br>“There’s a lot to be learned from the principles of protein restriction about how we would manage aging, and aging well,” says Stuart Phillips, a physiologist at McMaster University in Hamilton, Canada.<br>The mouse food diaries<br>Protein restriction, Phillips says, is a sort of “lite” version of a more well-known longevity hack — caloric restriction. Cutting overall calories eaten, typically by 20 percent to 50 percent, has been linked to long lifespan in lab animals since more than a century ago. Some dedicated humans are trying a milder version.<br>Lab animals on low-calorie or low-protein diets are indeed long-lived. In one recent study, mice that ate all they wanted of normal chow lived for a maximum of 1,008 days. Mice given the same food, but only 80 percent of the calories, survived for up to 1,179 days — a ripe old age for a mouse. Those sets of mice received chow with 18 percent protein, but a third group feasted on an all-you-can-eat buffet with only 6 percent of calories from protein. Their survival was in between the others, with a maximum of 1,115 days.<br>These effects went beyond long life; restrictive diets also improved health. Mice on calorie-restricted or protein-restricted diets had lower levels of sugar and insulin in their blood, and lower insulin sensitivity — markers of metabolic fitness. These healthy signals continued as the mice on restrictive diets grew older, while their status deteriorated in the aging mice that ate normally. Not surprisingly, the mice on calorie- or protein-restricted diets also had lower body fat. Indeed, at a one-year check-in, they were downright gaunt, weighing in at about two-thirds the mass of their normally dining counterparts.

Researchers fed 30 male mice a standard diet with 20 percent protein, and 30 additional mice a diet with only 5 percent protein. Those that got less protein lived longer.

In another recent study, researchers zeroed in on molecular signs of aging. As animals get older, their bodies undergo changes, such as the damage of tissues by unstable free oxygen radicals. Mice on a low-protein diet exhibited a variety of anti-aging features, in their DNA and proteins, across multiple organs. For example, they boosted levels of protective, antioxidant enzymes....