Adults can lose muscle as they grow older, but New York based fitness coach Jacob Zemer says several straightforward habits can help preserve strength and mobility. The issue has gained added attention as more Americans use GLP-1 medications, which have been linked to lean muscle loss, particularly during rapid weight loss.

Zemer, who primarily trains clients between 35 and 55 years old, said changing lifestyles are a major factor. “The biggest change is lifestyle,” he told Fox News Digital. “When you're in your teen years or your 20s, you're running around, you're doing activities that lend themselves to building muscle.”

That pattern often changes as adults devote more attention to careers and families. “You simply become more sedentary, which lowers your metabolism and your level of activity, so you're going to have less muscle.”

Hormone levels also begin changing for men and women as they approach their 40s, according to Zemer. He said this affects how the body uses calories, with less going toward protein and muscle building and more being stored as fat.

“We see this all the time … people start to store fat in their tummies, and they start have less muscle.” Zemer said people should be “very mindful” about building muscle beginning at a young age.

He compared muscle built before the later decades of life to financial savings. “All the way up into your 50s, your goal should be to build muscle so that when you enter your golden years — your 60s, 70s, 80s — it's kind of like your 401K,” he said.

The first habit is consuming enough protein, which helps stimulate muscle protein synthesis, the body’s process of repairing and building muscle. Adequate protein intake can also help reduce the risk of sarcopenia, the loss of muscle mass and strength that occurs with age.

Protein requirements can vary based on a person’s age, activity level and fitness goals. Zemer said sedentary adults do not need to become preoccupied with protein, but people who train regularly may benefit from consuming between 0.8 and 1 gram of protein per pound of body weight.

Strength training is another important part of preserving muscle. The U.S. Physical Activity Guidelines recommend that adults perform strength exercises at least two days each week and work the legs, hips, back, abdomen, chest, shoulders and arms.

The Centers for Disease Control and Prevention advises exercising at moderate or greater intensity until completing another repetition with good form becomes difficult. The guidelines also recommend 150 to 300 minutes of moderate intensity aerobic activity or 75 to 150 minutes of vigorous activity each week.

Zemer emphasized that lifting weights can preserve existing muscle even when a workout routine is not sufficient to build more. “Even if you have a busy week, and you went to the gym and you lifted weights 30 minutes twice a week, that may not be enough to build new muscle , but that is certainly enough to maintain muscle,” he said.

Beginners can start with functional movements that support everyday activities. Zemer recommended body weight exercises such as squats, lunges, push ups and pulling movements, along with carrying weighted objects in an exercise known as a farmer’s carry.

Carrying weights can help improve grip, balance and overall stability, according to Zemer. People who feel intimidated by the gym may also benefit from working with a qualified trainer for a few sessions to improve technique and confidence.

Quality sleep is another key strategy, although Zemer said it may be the most difficult one to maintain. He recommended seven to nine hours and noted that occasionally missing that target does not mean a person will lose muscle.

Persistent and serious sleep deficiency is more concerning. “But when you start to look at actual serious sleep deficiency, like we're talking five hours consistently, that is when you see rapid muscle loss.”

Regular movement also matters, even when a person cannot complete a structured workout. Zemer cautioned against becoming completely inactive and said movement can help slow muscle loss, while sedentary behavior is associated with rapid declines in muscle mass and strength.

“The worst thing you can do, even if you're injured, is to stop doing anything,” Zemer said. “Find things you can do. Even if something hurts you, even if your knees aren't like what they used to be.”

These habits are especially important for people taking GLP-1 medications for weight loss, Zemer said, because muscle loss can occur without strength training or adequate protein. “You want to make sure you're getting that protein and training, so that you are not losing muscle on top of the fat loss.”