Major Study Questions High-Protein Diets for Sedentary Adults

A major scientific review published July 31 in Cell Press Blue examined over 350 studies and found that eating less protein may slow aging and extend lifespan, especially for sedentary people. The finding challenges the booming high-protein food market and conflicts with updated US dietary guidelines that nearly doubled protein recommendations to 1.2 to 1.6 grams per kilogram of body weight this year.

What the new research says about protein and aging

Pathologist Dudley Lamming at the University of Wisconsin-Madison led the review, which analyzed studies across humans, mice, insects, yeast, and other organisms. The research found that protein restriction turns on body processes linked to healthier aging and better metabolism. In rodent studies, animals eating the minimum recommended protein intake of 0.8 grams per kilogram of body weight lived more than 50% longer than those eating double that amount.

How protein restriction may extend lifespan

Protein restriction increases levels of the hormone FGF21, which acts on the brain, fat tissue, and liver to improve blood sugar levels and reduce senescent cells that accumulate with age and cause chronic inflammation. The restriction also dampens activity of a protein called mTORC1, which normally stimulates aging processes. Clinical trials in humans have shown that reducing protein intake can reduce weight and fat mass and improve fasting blood sugar, even when protein-restricted individuals eat more total calories.

The conflict with US dietary guidelines and market trends

The US updated its dietary guidelines this year, recommending an increase in daily protein intake to 1.2 to 1.6 grams per kilogram of body weight, nearly doubling the previous 0.8 grams per kilogram recommendation. This shift came partly because some studies found that eating more protein could promote weight loss and reduce age-related muscle loss in older adults when paired with exercise. Meanwhile, 70% of US adults said they try to eat more protein, and high-protein diets ranked as the most popular diet type for the third consecutive year in 2025.

Why the science remains unsettled

Lamming notes that protein is essential for muscle growth and exercise response in active individuals, but most people are relatively sedentary and likely consuming more protein than needed. However, scientists caution that nutritional studies in animals like mice and rats do not always translate directly to humans. The research suggests that for sedentary adults who already meet minimum protein needs, additional protein offers little benefit and may carry metabolic risks.

Final Thoughts

The research suggests sedentary adults may not need the high-protein intake now marketed everywhere. For investors in food and supplement companies, the trend toward protein-fortified products faces headwinds from emerging evidence that less may be better for most people.

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