GLP-1 Drugs in Older Adults: What We Know About Muscle and Function

GLP-1-based therapies have transformed the treatment of obesity and type 2 diabetes. Semaglutide and tirzepatide can produce substantial weight loss, and large randomized trials have shown benefits that extend well beyond the scale. In SELECT, a trial of more than 17,000 adults with overweight or obesity and established cardiovascular disease but without diabetes, semaglutide reduced major cardiovascular events by 20% compared with placebo [1]. In FLOW, semaglutide also reduced major kidney outcomes and cardiovascular death among adults with type 2 diabetes and chronic kidney disease [2].

For older adults, however, successful weight loss raises an additional question: what is being lost along with the weight?

How GLP-1 Drugs Affect Body Composition

Substantial weight loss rarely consists entirely of fat. In a body-composition substudy of STEP 1, people taking semaglutide lost considerably more fat than lean tissue. Lean body mass declined, but it made up a slightly larger share of total body weight after treatment because fat loss was greater [3].

The same general pattern has been seen with tirzepatide. In the SURMOUNT-1 body-composition substudy, roughly three-quarters of the weight lost was fat mass and about one-quarter was lean mass [4]. A 2026 systematic review and meta-analysis reached a similar conclusion across the broader GLP-1 literature: fat loss generally predominates, although some lean tissue is also lost [5].

Do GLP-1 Drugs Cause Muscle Loss?

These findings are sometimes summarized as evidence that GLP-1 drugs cause muscle wasting. That goes further than the data suggest. The scans used in many studies measure lean mass, which is not the same thing as skeletal muscle. Lean mass also includes water, organs, connective tissue, and other fat-free tissue. Some lean-tissue loss is expected with substantial weight loss from diet or other approaches as well. The more important question is whether treatment leads to meaningful losses of strength, mobility, or physical function.

What We Know About GLP-1 Drugs and Muscle in Older Adults

That question becomes more important in later life, when muscle strength and physical reserve may already be declining. Yet direct evidence in older adults remains limited. A 2026 review found that relatively few studies had focused specifically on older adults. Across the broader literature, measures of muscle mass often declined, while the smaller number of studies that measured strength generally did not show a clear decline. The authors concluded that we still do not know whether older adults are uniquely vulnerable to clinically important muscle loss during GLP-1 treatment [6].

What Current Guidelines Recommend for Older Adults

The 2026 American Diabetes Association Standards of Care reflect this balance. The guidelines note that GLP-1 receptor agonists provide cardiovascular benefits in older as well as younger adults, but recommend particular caution when an older person already has unexplained weight loss or poor nutrition. They also advise watching for dehydration and excessive weight loss and emphasize adequate protein intake and strength or resistance exercise during intentional weight loss [7].

Preserving Muscle and Physical Function During Weight Loss

The goal, then, should not simply be a lower number on the scale. In later life, successful obesity treatment should improve heart and metabolic health while preserving the physical capacity needed for daily life.

Older-adult weight-loss trials conducted before the GLP-1 era support that approach. In a randomized trial of adults aged 65 years or older with obesity, combining weight loss with exercise improved physical function. Resistance training, alone or combined with aerobic exercise, also helped limit the loss of lean mass during weight reduction [8].

What GLP-1 Use Means for Assisted Living

For assisted living communities, the practical implication is not that GLP-1 therapies should be avoided. It is that weight should be interpreted alongside function. A resident who loses 20 pounds may be healthier if heart and metabolic health improve, but clinicians and caregivers should also pay attention to appetite, nutrition, strength, mobility, falls, and the ability to perform everyday activities.

Balancing the Benefits of GLP-1 Drugs With Healthy Aging

GLP-1-based therapies offer important benefits for conditions that can shorten healthy life. The next phase of the evidence needs to answer a more age-specific question: can we preserve those benefits while also preserving the strength and physical reserve that support independence?