It’s no secret that your body composition changes as you get older.So you undoubtedly know about age-related bone loss, which can lead to osteoporosis (or its precursor osteopenia) if it becomes severe enough.But are you aware that a similar phenomenon can happen to your muscles?

It’s called sarcopenia, which is a loss of muscle mass that occurs with aging.

If you haven’t heard of it, don’t feel bad. “Many clinicians don’t even know what sarcopenia is,” says Roger A. Fielding, senior scientist at the USDA Human Research Center on Aging at Tufts University in Boston.

“It really means age-related loss in skeletal muscle mass and function or weakness that develops as a result.”

This can lead to decreased muscle strength and power, problems with mobility and balance, and decreased activity levels.

Sarcopenia is believed to affect 30 percent of people over 60, and more than 50 percent of those over 80. The best ways to diagnose it are with dual-energy X-ray absorptiometry (a DEXA scan), measures of walking speed, and handgrip strength.

People who are obese are particularly at risk, as are those who have insulin resistance, Type 2 diabetes, kidney disease, or hyperthyroidism.

Making matters worse, muscle loss and bone loss often go hand-in-hand, which can put you at serious risk for falls and fractures.

Sarcopenia also can ratchet up your odds of developing Type 2 diabetes and other metabolic disorders since muscle tissue helps your body regulate and use blood sugar, notes Douglas Paddon-Jones, professor of nutrition and metabolism at the University of Texas Medical Branch in Galveston.

“The thing about sarcopenia is it’s a slow, insidious process — it sneaks up on people,” he says.

While some age-related loss in muscle mass may be inevitable — people typically lose up to 1 percent per year after age 35 — “the progression of muscle loss to the point that quality of life and independence are impacted is not inevitable,” notes Thomas Lang, professor of radiology and biomedical imaging at the University of California, San Francisco.

Here are four ways to prevent, halt, or even reverse age-related muscle loss:

1. Keep moving. “People who are lifelong exercisers and continue to stay physically active [as they get older] tend to lose less muscle than people who are sedentary,” Fielding says. Even an activity as simple as walking for 30 minutes four times per week can make a substantial difference in muscle maintenance.

2. Eat enough protein. Research from the University of Texas Medical Branch in Galveston suggests that 25–30 grams of protein in each meal can stimulate muscle protein synthesis, thus preserving muscle mass as you get older. The amino acids in protein provide “the building blocks to continue to build and repair muscle,” Paddon-Jones explains. Consuming the essential amino acid leucine (present in lean meat, fish, and soy foods) also may help with muscle maintenance.

3. Get vitamin D levels checked. This can be done with a simple blood test, ordered by your doctor. If your vitamin D level is low, taking a supplement of vitamin D with calcium can help with muscle protein synthesis (talk to your doctor about how much vitamin D you should take).

On a side note, consuming omega-3 fatty acids (from fatty fish like salmon, tuna, and sardines, as well as walnuts and flaxseeds) may be helpful for muscle maintenance. The reason: When you have inflammation in the body, “inflammatory proteins take a toll on muscle mass, strength, and function,” Fielding explains.

4. Do resistance training. If you lift weights or use resistance bands or kettlebells two to three times per week, you can get substantial improvements in muscle mass over three to six months, Fielding says.

This is true even if you’ve already lost some muscle mass and function because resistance exercises stimulate protein synthesis, resulting in increased muscle mass and strength. But you need to do it regularly to reap these muscle-building, muscle-preserving benefits.