Why Muscle Matters as You Age: Strength, Protein and Staying Independent

Ask people what they want from the second half of life and you'll hear some version of the same answer: to stay independent. To carry their own luggage, get up off the floor after playing with grandchildren, climb the stairs at a friend's lake house, and travel without worrying about it.

Researchers who study aging increasingly point to one tissue underneath all of that: skeletal muscle. Here is what the published research says about muscle, protein and strength training as we get older, and where the evidence is still thin.

Muscle changes with age, and strength changes faster

The gradual loss of muscle mass and function with age has a name: sarcopenia. A widely used European consensus, updated in 2019, describes it as a progressive muscle disorder that is associated with falls, fractures, physical disability and death. Notably, that consensus now treats low muscle strength as the main warning sign, with low muscle mass used to confirm a diagnosis.

How fast? A 2012 quantitative review in Frontiers in Physiology pulled together decades of studies. Comparing younger and older groups, the median reported loss was about 0.47 percent of muscle per year in men and 0.37 percent in women. Studies following the same people found that around age 75, muscle mass fell roughly 0.8 to 1 percent a year in men and 0.6 to 0.7 percent in women.

Strength declined faster: about 3 to 4 percent a year in men and 2.5 to 3 percent in women at around 75, or two to five times faster than mass where both were measured. The authors concluded that losing strength was a more consistent risk factor for disability and death than losing mass.

Those are averages, and individuals vary widely. But the direction is clear, which makes muscle a fair topic in your 40s and 50s, not just your 80s.

Strength and independence: what the cohort studies show

Several large long-term studies have found that stronger people tend to fare better later in life. These are observational studies: they show associations, not proof that strength itself causes the better outcomes, and overall health may explain part of the link.

• Midlife strength and later disability. In the Honolulu Heart Program, researchers measured the hand-grip strength of 6,089 healthy Japanese-American men aged 45 to 68 between 1965 and 1970, then assessed survivors about 25 years later. Men in the lowest third for grip strength had about 2.9 times the odds of very slow walking speed compared with those in the top third, and more than twice the risk of self-care disability, after adjusting for other factors.
• Strength and mortality in older adults. In the Health, Aging and Body Composition study of more than 2,200 adults aged 70 to 79, lower leg and grip strength were associated with higher mortality over about five years. Muscle size on its own was not.
• A global picture. The PURE study followed nearly 140,000 adults in 17 countries for a median of four years. Each 5-kilogram lower grip strength was associated with a 16 percent higher risk of death from any cause, a stronger predictor than systolic blood pressure in that study.

None of this means a strong handshake guarantees anything. It does suggest strength is a useful marker of how the body is holding up, and one people can work on directly.

Protein: the research on how much older adults may need

The U.S. recommended dietary allowance for protein is 0.8 grams per kilogram of body weight per day for adults generally. Two expert groups focused on older adults have suggested more.

• PROT-AGE (2013). An international study group convened by the European Union Geriatric Medicine Society recommended that healthy adults over 65 average at least 1.0 to 1.2 grams of protein per kilogram of body weight per day, at least 1.2 g/kg for those who exercise or are otherwise active, and 1.2 to 1.5 g/kg for most older adults with acute or chronic illness.
• ESPEN (2014). The European Society for Clinical Nutrition and Metabolism's expert group reached similar numbers: at least 1.0 to 1.2 g/kg for healthy older people, 1.2 to 1.5 g/kg for those at risk of malnutrition because of illness, plus daily activity and resistance training where possible.

To put that in everyday terms: at 1.0 to 1.2 g/kg, a person weighing 75 kilograms (about 165 pounds) would be looking at roughly 75 to 90 grams of protein a day.

An important exception. Both groups flag kidney disease. PROT-AGE notes that older adults with severe kidney disease who are not on dialysis may need to limit protein. If you have kidney disease, or any condition that affects your diet, talk with your doctor before raising your protein intake.

Per meal, not just per day

Research also looks at how protein is spread across the day. Many people eat most of theirs at dinner. PROT-AGE describes a per-meal "anabolic threshold" that appears higher in older adults than in younger ones: about 25 to 30 grams of protein per meal, containing roughly 2.5 to 2.8 grams of leucine, an amino acid that helps switch on muscle-building signals. The group was careful to note that evidence on timing and protein quality was not yet strong enough for firm recommendations.

In a small, frequently cited 2014 study, eight healthy adults (average age about 37) ate the same total protein either evenly, about 30 grams per meal, or skewed toward dinner. Muscle protein synthesis over 24 hours was about 25 percent higher with the even pattern. Eight people for a week is suggestive, not settled.

Protein's partner: resistance training

Protein on its own is only half the story. The research consistently pairs it with muscle-strengthening exercise.

• Training works at older ages. A 2011 meta-analysis of 49 studies in adults 50 and older found resistance training added about 1.1 kilograms of lean mass on average, with larger gains from higher-volume programs and somewhat smaller gains in the oldest participants.
• Protein can add to training. A 2018 meta-analysis in the British Journal of Sports Medicine found protein supplementation modestly increased training gains in strength and muscle, leveling off at total intakes around 1.6 g/kg per day. The effect was smaller in older adults, possibly because older participants received relatively low doses.
• The official guideline. The U.S. Physical Activity Guidelines for Americans recommend muscle-strengthening activities involving all major muscle groups on two or more days a week for adults, and for older adults, a mix that also includes aerobic and balance activities.

Try this: a two-week muscle check-in

These are small, low-risk steps for a healthy adult. If you have kidney disease, heart disease or another chronic condition, or haven't exercised in a while, check with your doctor first.

• Look at breakfast. For one week, note roughly how much protein each meal contains, using food labels or a free nutrition app. Many people discover breakfast is the light one. Try building it around a protein-rich food such as eggs, Greek yogurt, cottage cheese, fish or tofu.
• Book two strength sessions a week. Put them on the calendar like meetings. Bodyweight moves such as sit-to-stands from a chair, wall push-ups and step-ups are a reasonable start; a qualified trainer or physical therapist can tailor a plan.
• Pick a simple marker. Count how many times you can stand up from a chair, without using your arms, in 30 seconds. Check again in a month. It's not a diagnosis, just a way to notice change over time.

Muscle won't stop the calendar. But the research ties it closely to what most of us care about: moving freely, staying capable and living on our own terms.

Sources

• Cruz-Jentoft, A. J., et al. (2019). Sarcopenia: revised European consensus on definition and diagnosis. Age and Ageing, 48(1), 16–31. PubMed
• Mitchell, W. K., et al. (2012). Sarcopenia, dynapenia, and the impact of advancing age on human skeletal muscle size and strength; a quantitative review. Frontiers in Physiology, 3, 260. PubMed · Full text
• Rantanen, T., et al. (1999). Midlife hand grip strength as a predictor of old age disability. JAMA, 281(6), 558–560. PubMed
• Newman, A. B., et al. (2006). Strength, but not muscle mass, is associated with mortality in the Health, Aging and Body Composition Study cohort. Journals of Gerontology: Series A, 61(1), 72–77. PubMed
• Leong, D. P., et al. (2015). Prognostic value of grip strength: findings from the Prospective Urban Rural Epidemiology (PURE) study. The Lancet, 386(9990), 266–273. PubMed
• Bauer, J., et al. (2013). Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. JAMDA, 14(8), 542–559. PubMed
• Deutz, N. E., et al. (2014). Protein intake and exercise for optimal muscle function with aging: recommendations from the ESPEN Expert Group. Clinical Nutrition, 33(6), 929–936. PubMed · Full text (PMC)
• Mamerow, M. M., et al. (2014). Dietary protein distribution positively influences 24-h muscle protein synthesis in healthy adults. Journal of Nutrition, 144(6), 876–880. PubMed
• Peterson, M. D., Sen, A., & Gordon, P. M. (2011). Influence of resistance exercise on lean body mass in aging adults: a meta-analysis. Medicine & Science in Sports & Exercise, 43(2), 249–258. PubMed
• Morton, R. W., et al. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine, 52(6), 376–384. PubMed
• U.S. Department of Health and Human Services (2018). Physical Activity Guidelines for Americans, 2nd edition. PDF
• National Academies (2005). Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (protein RDA of 0.8 g/kg/day for adults). National Academies Press
• CDC. 30-Second Chair Stand test (STEADI). PDF