Menopause, Muscle, and Metabolism

Muscle is about more than a toned body. Its metabolic prowess is the cornerstone of good health.

Photo by Alexandra Tran on Unsplash

There’s a lot of buzz about making muscle in midlife, and for good reason. About 30% to 40% of an adult’s body is skeletal muscle mass, and we should do what everything possible to keep it that way.

You also have two other types of muscle: the cardiac kind, found only in the heart, and smooth muscle, found in organs, blood vessels, skin, and other areas of the body. Skeletal muscle is by far the most metabolically active type of muscle and the only kind that’s under your control.

In addition to communicating with the rest of the body to help regulate metabolism, skeletal muscle stores energy as glycogen and stockpiles amino acids, the building blocks of cells, enzymes, hormones, and all the other compounds that keep you alive.

What Happens to Muscle in Midlife

For the first three decades of life, you accumulate muscle mass on a steady basis until about age 30 when it begins to slowly decline. Once you’re 65, muscle loss accelerates. Sarcopenia is the decline of muscle tissue. It can occur at any time of life or with chronic illness but it’s most often linked to the aging process.

Menopause contributes to sarcopenia, as lower levels of estrogen in the body promote inflammation and other changes, such as the build-up of fat within muscle tissue, that lead to less skeletal muscle and a reduction in muscle function and strength. Visceral fat, which tends to accumulate in midlife or whenever menopause occurs, is also related to declines in skeletal muscle.

Sarcopenia can cause weakness, fatigue, and difficulty performing everyday tasks. And that’s not all. Sarcopenia is a progressive condition tied to long-term health in a number of ways, including a reduction in cognitive skills and a greater risk for dementia.

Muscle Is A Metabolic Machine

Skeletal muscle helps you move around, protects your internal organs, and holds joints in their proper positions. Though all of these functions are laudable, muscle’s role in reducing the risk for chronic conditions could be considered its crowning glory.

More muscle can make weight control easier. I say “may” because while it’s true that muscle requires more calories to maintain than fat tissue, the difference is minimal. A pound of fat tissue burns about two to three calories daily while the same amount of muscle burns about six calories per day at rest. It’s likely that the calories used working out to create muscle – the actual physical activity itself - is the primary reason for easier weight control. Adding muscle could provide a slight calorie-burning edge, but it’s not a magic bullet. 

That’s not to say you shouldn’t try to keep the muscle you have, make more muscle, or both. On the contrary. Maintaining adequate muscle mass can help you avoid health problems now and down the road by heading off metabolic issues including insulin resistance.

Insulin is a hormone that facilitates the movement of glucose from the blood into cells by acting like a key that allows glucose inside. Insulin resistance happens when cells are unable to efficiently link up with insulin, resulting in chronically elevated blood glucose levels. Insulin resistance is associated with a higher risk for several chronic illnesses, including overweight and obesity, prediabetes, type 2 diabetes, high blood pressure, cardiovascular disease, cancer, and liver disease.

Skeletal muscle tissue uses the lion’s share of glucose and is largely responsible for maintaining normal blood glucose concentrations. Low muscle mass can make for a higher blood glucose level, forcing the body to constantly try to lower it by pumping out more insulin.  However, as time goes on, the pancreas becomes overworked and blood glucose levels remain in the danger zone.  

Here’s another marvelous thing about muscle. In addition to using large amounts of glucose with an assist from insulin, muscle cells are also capable to taking up glucose from the blood without insulin, which happens when you exercise.

Photo by Jeffrey Grospe on Unsplash

Strength Training Supports Muscle Mass

The body is constantly making new muscle cells and breaking down older ones. Some muscle loss is inevitable as cell breakdown overtakes cell production as a result of aging.  However, inactivity, particularly a lack of muscle-strengthening exercise (resistance training), plays a major role in reduced muscle mass and strength.

Muscle-strengthening exercises maintain and build muscle mass.  The Physical Activity Guidelines for Americans (PAG) suggests participating in muscle-strengthening exercises that target all of the major muscle groups on two or more separate days weekly. Muscle-strengthening exercises include training with free weights, machines, or bands, or using your own body weight to create resistance.

I grew up during a time when cardio was king, and strength-training was an afterthought. That thinking has changed. A 2022 British Journal of Sports Medicine review found that 30 to 60 minutes a week of resistance training was associated with a lower risk for cardiovascular disease, diabetes, lung cancer, and death from any cause in adults 18 and older. 

In addition to improved glucose uptake in the short-term, it’s worth noting that physical activity can lower your blood glucose levels for up to a day, or even more, after working out. And, among its many other benefits, exercise protects skeletal muscle by helping to prevent the accumulation of fat within muscle tissue.

Don’t shun aerobic activities for strength training, though. A combination of both types of exercise is best. The PAG says healthy adults should include at least 150 minutes of moderate-intensity aerobic activity, such as brisk walking, jogging, or biking every week (about 30 minutes on most days).

One of the best aspects of exercise is that it’s possible to reap health benefits from exercise no matter what your age, size, or level of ability. There’s a lot of talk on social media about “lifting heavy.” If you haven’t worked out for a while, or you have a chronic condition, such as arthritis, osteoporosis, or high blood pressure, you should NOT begin exercising using heavy weights or any other high level of resistance. (You should also consult your doctor first.) The idea is to challenge your muscles to get them to grow. Start slowly and continue to build up. There’s no point in injuring yourself to make more muscle!

Photo by Elizabeth Ward

Diet and Exercise: A Winning Combination for Muscle

What you eat is just as important as exercise for making muscle. Optimizing protein intake at every meal and including foods with complex carbohydrates and healthy fats is key to skeletal muscle production and preservation. 

In my experience, midlife women tend to come up short for protein on a regular basis, and by that I mean they don’t even satisfy the current U.S. recommended intake for protein every day, which is 0.8 grams per kilogram (kg) of body weight (about .36 grams per pound). What’s worse is that many protein researchers contend that the suggested protein intake for adults are too low to protect aging muscle.  

Some experts suggest that women ages 50 and older should consume 1 to 1.2 grams of protein per kg daily to support muscle and bone mass. It’s a good idea to err on the higher side of that recommendation, especially if you are physically active. For a 150-pound woman (68 kg), the higher end amounts to about 81 grams of protein per day.

It’s next to impossible for healthy adults to build muscle tissue without pairing strength exercises with proper nutrition, so consider them partners.  My next post will cover protein in more detail, so look for that coming soon!

Questions? Ask me in the comments!