If you’re big on protein, you might have heard about the recent review of more than 350 studies published in Cell Press Blue that found eating less protein may improve metabolism, reduce cellular damage, and in some cases extend lifespan.
But wait a minute…if you read past the headline, you’ll soon discover that the research findings were more related to who was involved, not protein itself. Most of the strongest data came from mice, flies, and yeast, and the majority of human data came from people who don’t strength train.
The review’s own corresponding author, Dudley Lamming, Ph.D., of the University of Wisconsin-Madison, said as much in the press release, calling it “absolutely crystal clear that there are benefits of protein to muscle growth” in active people, and pointing out that the overconsumption problem occurs mainly when people are sedentary.
Below, dietitians walk through the four reasons why the headline’s findings don’t carry over to men who lift, and what does instead.
Why the Strongest Evidence Comes From Mice, Not Men
Lifespan studies are brutally hard to run in humans. Researchers need decades of studying and tight control over what thousands of people eat, so for studies that need years to come to a conclusion, researchers lean on organisms that die on a convenient schedule.“The longest controlled metabolic studies on humans included in this paper are about six weeks long and were done on metabolically unhealthy, sedentary, obese, or aging populations–not healthy, resistance-trained subjects,” says registered dietitian Paul Kriegler, RD. “The strongest protein restriction data comes from rodents, not humans.”
The Human Data Studied Guys Who Don’t Train
Beyond short study durations, the human data comes with major caveats regarding real-world eating habits and exercise. In human trials, the low-protein groups consumed about 0.8 grams per kilogram of body weight, which matches the bare minimum daily recommendation. That level is vastly different from the extreme protein cuts tested in animal models, and it fails to reflect how active people actually live or train.“The doses don’t match. Table 1 of the review lists rodent restriction arms at 4 to 10 percent of calories from protein, compared with controls at 19 to 75 percent. No human eats at the low end of that,” says David Goldman, MS, RDN, CSCS, FAND, a visiting researcher at the University of Helsinki. “High protein intake in an epidemiological dataset describes a dietary pattern. It says nothing about training history.”
Related: 18 Dietitian-Approved Foods to Help You Hit Your Protein Goals and Stop Mid-Day Cravings
How Exercise Completely Changes How Your Body Uses Protein
That lack of training history matters because physical activity fundamentally alters how your body processes every gram of protein you eat. In a sedentary person with no muscle damage to repair, surplus amino acids trigger growth signaling pathways like mTORC1 and IGF-1, which researchers link to faster cellular aging. In an active person, those same amino acids are funneled straight into tissue recovery instead of lingering in the bloodstream.
“Protein is also a bit unique in that unlike carbohydrates and fats, the body does not have a dedicated efficient storage for excess amino acids,” explains Alexander LeRitz, MSc, RDN, CDN, CNSC, CPT, a sports nutritionist at JM Nutrition.
Without a designated storage tank for extra protein, physical movement becomes the ultimate deciding factor in how those amino acids behave inside your cells.
“Trained muscle is more sensitive to a given dose of amino acids and directs them toward repair and remodeling,” explains Goldman. “In an inactive person, surplus amino acids get oxidized or feed the growth signaling described in the review.”
Does Protein Matter More After 65?
Protein is essential at any life stage, but especially after age 65 when age-related muscle loss accelerates. In fact, the researchers behind the review paper pointed out that many older adults actually eat too little protein, not too much.
However, the underlying reason older adults need higher protein intake comes down to a shift in how the body processes nutrients. As you age, your muscles become less responsive to amino acids, requiring roughly 68 percent more protein in a single sitting to fully trigger muscle repair. For a 180-pound adult, that means aiming for about 33 grams of protein per meal rather than 20.
“Anabolic resistance correlates more closely with inactivity and body fat than with age,” Goldman notes. “Keep training, stay lean, and your daily total may not need to go up much. Just put more of it on each plate.”
What Daily Target Should You Actually Aim For?
Determining your personal protein intake depends far more on your training intensity and goals than on general population averages.
“For someone training hard and chasing maximum gains in strength and size, consuming approximately 1.6 grams of protein per kilogram of bodyweight per day is an appropriate target,” Goldman says. “For someone lifting a few times a week to stay strong and healthy, it’ll be totally fine to eat considerably less protein.”For a 180-pound adult male, 1.6 g/kg works out to roughly 130 grams a day. If you lift twice a week for strength, research says you don’t need as much. However, if you’re dieting to get lean, you should aim for 1.6 g/kg.
“Once your protein needs are met, pushing substantially higher does not appear to provide any additional muscle-building benefit and may in fact push out opportunities for other nutritious foods that contain vitamins and minerals necessary for optimal health,” LeRitz explains.
What This Means for Your Daily Diet
While the findings suggest that restricting protein might slow cellular aging, those conclusions stem largely from animal models and sedentary human populations. For active individuals, particularly those who lift weights, the rules are entirely different. Strength training directs the amino acids you eat straight into muscle repair rather than activating the growth signaling pathways tied to accelerated aging.
Targeting roughly 1.6 grams of protein per kilogram of body weight daily remains a solid benchmark for building muscle, while lifting a couple of times a week for general health requires noticeably less. Anyone managing conditions like kidney disease should consult a physician before making major dietary adjustments.
Sources
Knopf B, Lamming D. The hallmarks of protein and amino acid restriction in aging and longevity. Cell Press Blue, 2026; 1
Hoy, M. Katherine, et al. “Protein Intake of Adults: What We Eat in America, NHANES 2015-2016.” FSRG Dietary Data Briefs, United States Department of Agriculture (USDA), January 2021.
Murphy, Caoileann H et al. “Nutrition strategies to counteract sarcopenia: a focus on protein, LC n-3 PUFA and precision nutrition.” The Proceedings of the Nutrition Society vol. 82,3 (2023): 419-431. doi:10.1017/S0029665123003555
Nishimura, Yusuke et al. “Dietary protein requirements and recommendations for healthy older adults: a critical narrative review of the scientific evidence.” Nutrition research reviews vol. 36,1 (2023): 69-85. doi:10.1017/S0954422421000329
Deane CS, Cox J and Atherton PJ (2024) Critical variables regulating age-related anabolic responses to protein nutrition in skeletal muscle. Front. Nutr. 11:1419229. doi: 10.3389/fnut.2024.1419229
Nunes E. A., Colenso-Semple L., McKellar S. R., Yau T., Ali M. U., Fitzpatrick-Lewis D., Sherifali D., Gaudichon C., Tomé D., Atherton P. J., Robles M. C., Naranjo-Modad S., Braun M., Landi F., and Phillips S. M. (2022) Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults, Journal of Cachexia, Sarcopenia and Muscle, 13, 795–810,
Zilova, I S, and E N Trushina. Voprosy pitaniia vol. 92,4 (2023): 114-124. doi:10.33029/0042-8833-2023-92-4-114-124
Experts
Dudley Lamming, Ph.D., of the University of Wisconsin-Madison
David Goldman, MS, RDN, CSCS, FAND
Alexander LeRitz, MSc, RDN, CDN, CNSC, CPT, a sports nutritionist at JM Nutrition.
This story was originally published by Men’s Journal on Oct 19, 2026, where it first appeared in the Fitness section. Add Men’s Journal as a Preferred Source by clicking here.