Muscle Matters: Beyond Biceps and Brawn

You may associate muscle with six-pack abs, bulging biceps and exceptional feats of strength, but it does much more than provide a toned body. Skeletal muscle makes everyday movement possible, including grocery shopping, gardening and getting out of bed, and its metabolic prowess takes on new meaning as you age.

Between 30% to 40% of the body is skeletal muscle, which is connected to bones and allows you to move on command and protects your joints by holding them in place. According to the National Institutes of Aging, muscle mass increases from birth to age 30 to 35. After that, muscle maintains a slow and steady decline until age 65 for women and 70 for men, when loss accelerates.

Sarcopenia, characterized by muscle tissue loss caused by aging and other factors, is linked to weakness, fatigue and difficulty with everyday activities. It's also tied to your health in several ways.

Every cell in the body requires energy in the form of glucose. After a meal or snack, the pancreas releases insulin, a hormone that facilitates the movement of glucose from the bloodstream into the cells. Given its sheer mass, skeletal muscle guzzles the most glucose and is mainly responsible for maintaining average blood glucose concentrations. 

Therefore, low skeletal muscle can result in elevated blood glucose levels that the body repeatedly tries to reduce by releasing more insulin. With time, this scenario can cause insulin resistance, a condition linked to type 2 diabetes, high blood pressure, cardiovascular disease and nonalcoholic fatty liver disease.

Less muscle causes metabolic mayhem, and excess belly fat exacerbates it. Men and women tend to accumulate more fat around the midsection with age. Belly fat, technically visceral fat, spells trouble for muscle tissue.

"Visceral fat secretes hormones and other compounds that negatively affect muscle in several ways," says Douglas P. Kiel, M.D., professor of medicine at Harvard Medical School and director of the Musculoskeletal Research Center. 

Kiel was one of the authors of a 2022 study that found people with the most significant six-year visceral fat accumulation had significantly lower muscle density surrounding the spine. Low muscle density is linked to reduced muscle function.

The brain may also suffer from muscle loss. For example, a 2022 study involving nearly 8,300 older adults over three years found low muscle mass was associated with a decline in executive functions, which include problem-solving, attention and working memory. One reason for the link is that muscle releases beneficial compounds for tissue regeneration and repair and facilitates communication between brain cells.

While some loss of skeletal muscle loss is unavoidable with age, it's possible to preserve and produce muscle tissue in midlife and beyond. "Regular exercise results in larger muscle fibers, better coordination, better synchronization from the nerves to muscle contraction and better insulin glucose uptake from the muscle," Kiel says.

Resistance training, also called strength training, is particularly important to offset age-related muscle decline. Resistance training activities include weightlifting with machines or free weights, resistance bands, and activities that use your body weight, including yoga, pushups and squats.

A recent review of 16 studies found that resistance training was associated with a decreased risk for cardiovascular disease, diabetes, lung cancer and death from any cause in adults 18 and older. Just 30 to 60 minutes weekly was enough to produce positive results. 

The Physical Activity Guidelines for Americans suggest muscle-strengthening exercises on two or more days weekly in addition to at least 150 minutes of moderate-intensity aerobic activity, such as brisk walking, spread throughout the week.

The good news is that you don't have to join a gym or do complicated workouts to get or stay fit. "People over 50 should preserve muscle mass by eating a well-rounded diet with protein and doing exercises of any kind such as walking or simple weightlifting," says Kiel.

People should engage in regular physical activity according to their abilities and avoid inactivity as much as possible. Check with your doctor before changing your physical activity, particularly if you have certain chronic health conditions such as osteoarthritis, osteoporosis, high blood pressure or a disability that may limit movement.

A balanced eating plan and regular exercise work together to protect against muscle tissue loss, according to Leslie Bonci, M.P.H., R.D., a sports dietitian and owner of Active Eating Advice. She suggests putting protein front and center on the plate, particularly as you age. 

"Optimizing protein intake at every meal while including enough carbohydrate and healthy fat is key to skeletal muscle production and preservation," she says.

Regarding protein, many older people are behind the eight ball. About half of all women and 30 percent of men 71 and older living in the U.S. fall short of protein recommendations. To make matters worse, many researchers say the current suggested protein intake is too low to protect aging muscle. In addition, experts argue that total protein intake isn't enough — you must also keep leucine in mind.

Leucine is an amino acid in food that's notable for its ability to stimulate muscle cell production. Research suggests eating at least 25 to 30 grams of protein and 2.5 grams or more of leucine at every meal hedges against the loss of muscle loss.

That amount of protein may sound overwhelming, but Bonci says it's easy to assemble meals and snacks with muscle-making in mind. "The good news is that certain high-protein foods have a significant amount of leucine," she says. Four ounces of cooked meat, poultry, or seafood supplies about 2.5 grams of leucine and 20 to 30 grams of protein. Other protein-rich foods with leucine include plain Greek yogurt, cottage cheese, and milk.

If you can't eat enough food to satisfy your protein needs, Bonci suggests whey protein powder, which is rich in protein and leucine, to bump up nutrition in meals and snacks without increasing the amount of food. Add whey protein powder to cooked oats, smoothies, sauces and soups. 

However, protein contains calories, and it may be necessary to cut back on low-nutrient foods, such as snack chips, ice cream and cookies, to accommodate more protein in your eating plan.

Elizabeth M. Ward is a registered dietitian nutritionist (RDN), writer, and award-winning nutrition communicator. Her work has appeared in WebMD, Men’s Health, and EatThis.com.

Ward is the author or co-author of eight nutrition, food, and health books. Her most recent book is The Menopause Diet Plan, A Natural Guide to Hormones, Health, and Happiness (co-author). Ward lives in the Boston, MA, area. Read More