By Jessica Starr and Emily Stein
For millions of Americans, GLP-1 medications have become an important tool for managing diabetes and obesity. But patients considering these drugs should understand that the number on the scale does not tell the whole story.
Rapid weight loss often comes with reductions in bone density and muscle mass, changes that can compromise strength and mobility while increasing fracture risk. For that reason, GLP-1 treatment should not be viewed as a stand-alone intervention. Patients can benefit from combining such medications with medical supervision, adequate nutrition, and a consistent program of resistance and weight-bearing exercise.
GLP-1 drugs act in part by imitating glucagon-like peptide-1, a naturally occurring hormone involved in appetite, digestion, and blood-glucose regulation. By increasing satiety and reducing appetite, these medicines generally cause people to consume less food, which can lead to weight loss
The results can be substantial. Depending on the medication and the patient, people may shed roughly 5% to 20% or more of their body weight over the course of a year. Some patients also experience meaningful cardiovascular benefits.
Yet not every pound lost comes from fat. Research suggests that roughly one-quarter of the weight people lose while taking these drugs may be attributable to losses in muscle and other musculoskeletal tissue.
For patients who are already vulnerable to frailty, that deserves attention. The issue may be especially relevant for women approaching or going through menopause. Falling estrogen levels experienced during this transition already contribute to declines in muscle and skeletal strength.
These considerations do not rule out GLP-1 medications for older adults, who may still derive substantial health benefits from them. But patients should understand the potential effects beyond weight loss and work with their physicians to minimize those risks.
The conversation should begin with a careful assessment of individual goals, expected benefits,
and potential downsides of treatment.
Exercise, especially strength training, should also be considered an integral part of the prescription rather than an optional add-on. Evidence suggests that pairing GLP-1 treatment with physical activity can help patients reduce body weight while better protecting muscle and bone.
Diet matters, too. Because people taking GLP-1s often consume substantially fewer calories, what they eat becomes even more important. Patients should discuss nutrition with their physicians and make sure they are getting adequate protein along with nutrients such as calcium, vitamin D, and magnesium that help support muscle and skeletal health.
The excitement surrounding GLP-1 medicines is understandable. Their beneficial effects appear to even extend beyond weight reduction and glucose control. Researchers are studying promising applications for a range of conditions including cardiovascular and kidney disease and osteoarthritis.
As GLP-1 use expands, the conversation around these drugs should expand with it. Patients should understand both the potential downsides and advantages of these medicines — and work with their physicians to prioritize their bone health and muscle strength during any course of treatment, instead of focusing on the number on the scale alone.
Jessica Starr, MD, is an endocrinologist at Hospital for Special Surgery. Emily Stein, MD, MS, is Co-Director of the Skeletal Health Orthopedic Research Program at Hospital for Special Surgery.
