Study
Eating less protein could slow aging: major review of 350+ studies
A University of Wisconsin-Madison review of over 350 studies finds that reducing protein intake activates the same longevity pathways as calorie restriction, even without cutting total calories.
Summary Could eating less protein help people age more slowly? Show / hide ↓
Researchers reviewed more than 350 studies of eating less protein or fewer specific amino acids, which are the building blocks of protein. In flies and mice, these diets sometimes extended lifespan and reduced inflammation, even when total calories stayed the same. A small number of human studies found possible improvements in body fat and blood sugar, but the results were not tested over decades of aging. The review also discussed mTOR, a cell growth system, and FGF21, a hormone that may help the body use energy when protein intake falls.
What this means for you: This review does not show that most people should eat less protein. Do not make major diet changes based on it, because much of the evidence comes from animals and the safest protein amount may differ for older adults, athletes, and pregnant people.
early evidenceResearchers at the University of Wisconsin-Madison, funded by the National Institute on Aging, reviewed more than 350 studies on protein restriction, amino acid restriction, and aging. The review found that lowering protein intake improved metabolism, reduced inflammation, and reduced cellular damage across multiple model organisms. Flies and rodents lived longer on protein-restricted diets even when their overall calorie intake did not decline. In human trials, participants who reduced protein lost body fat and improved fasting blood sugar, sometimes while consuming more total calories. The review identifies the amino acids methionine, isoleucine, and valine as particularly influential: excessive intake of these may activate growth pathways (notably mTOR) that accelerate aging. The hormone FGF21 emerged as a key mediator: it rises when protein intake falls, increasing energy expenditure and improving glucose regulation. Mice with elevated FGF21 lived longer, with stronger effects in males. The authors caution that protein needs are not uniform: athletes, pregnant women, and some older adults may benefit from higher intake. Updated US dietary guidance now recommends 1.2 to 1.6 grams per kilogram of body weight, nearly double previous recommendations.
Protein restriction may improve health and promote longevity through effects on metabolic function, nutrient signaling, and cellular damage, but guidance should be personalized by age and activity level.
The review acknowledges that evidence is not one-sided: higher protein intake supports weight loss and muscle preservation in older adults. The FGF21 effect was stronger in male mice than female mice, raising sex-specific questions. No single RCT proves that protein restriction extends human lifespan.
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