How prescription weight loss medication affects muscle loss and bone health

Key Points:

1. Losing weight can increase the risk of muscle and bone density loss, whether a person takes brand-name weight loss injection medication, compounded Semaglutide or Tirzepatide, diets or has weight-loss surgery.
2. Muscle mass and bone density changes make people more susceptible to falling, breaking bones and losing their independence—especially as they age.
3. Eating balanced, protein-rich meals and engaging in enjoyable physical activities (especially weight training or resistance exercises) encourage healthy weight management while on prescription weight loss medications.

Prescription weight loss medications can be transformative for people who struggle with their metabolism, medical conditions or other concerns.

But the metric used to determine who qualifies for medical weight loss—the body mass index, or BMI—doesn’t provide a complete picture of a person’s health. It doesn’t account for bone density, muscle mass, blood pressure or other factors that mark your health or risk of health conditions.

On the flip side, losing significant weight doesn't automatically make you healthier! Are you healthier if you shed pounds but don’t also shed joint pain, sleep issues, brain fog, low energy or heart disease risk?

Here, we explain how prescription weight loss medications affect muscle and bone health. Plus, how intentional fitness and eating practices can help you stay strong while you shed the pounds and negative habits that no longer serve you.

What are GLP-1 medications for weight loss?

GLP-1 is shorthand for the glucagon-like peptide-1 hormone naturally made in the body that slows digestion and controls appetite.

Medications like Semaglutide and Tirzepatide are GLP-1 receptor agonist medications. They mimic the GIP-1 hormone and increase its effect on hunger and digestion around the clock. (Tirzepatide additionally mimics the glucose-dependent insulinotropic polypeptide (GIP) hormone that also affects hunger and digestion.)

Semaglutide and Tirzepatide are safe and effective prescription weight loss treatments for adults with certain conditions. Semaglutide is the active ingredient in compounded Semaglutide, Ozempic®* and Wegovy®*. Tirzepatide is the active ingredient in compounded Tirzepatide, Mounjaro®* and Zepbound®*.

​​While GLP-1 medications can help some people eat less and lose weight, there are concerns about how they affect lean muscle and bone density.

Here’s what the research suggests.

How can GLP-1 medications cause muscle loss?

Weight loss happens when we expend more calories in energy than we take in by eating food. GLP-1 medications causes rapid weight loss.

The danger with rapid weight loss is that if we drastically reduce our calorie intake and don’t exercise, much of the weight we lose may come from fat and lean body mass—which includes muscle, fluid and bone mass. (Basically, everything but fat!)

In fact, studies suggest that 20% to 50% of overall weight loss for patients on GLP-1 medications can come from lean body mass.

This can cause a few issues:

If we lose weight on a prescription weight loss treatment but then stop it, we may regain weight that's made up of only fat. That means we’ll be in worse physical shape than before!

Our muscles help us sit, stand, move, maintain balance and perform everyday tasks. When we lose muscle mass, we lose strength and stability. Older adults, in particular, face an increased risk of falls, broken bones and hospital stays when they lose the muscles they need to keep stable.

So lowering body weight might help us reach health goals like lowering blood pressure, easing joint pain or improving heart health. But unintentional muscle mass loss might become an issue at the same time.

That’s why early research suggests exercising to maintain lean muscle while taking weight loss medications is the best way to encourage long-lasting weight management.

How do GLP-1s impact bone health?

More studies are needed in this area, too—especially those taking GLP-1 medications who don’t have type 2 diabetes. But researchers are already seeing that Semaglutide and Tirzepatide may affect bone health.

Bones can become less dense as we lose weight for any reason—even moderate decreases in weight can cause bone loss. But it’s especially true when we lose significant weight over a short period. This may be because when we eat less, we may take in less calcium and Vitamin D.

Also, increased GLP-1 and GIP levels slow the process by which food leaves our stomach. So these medications may affect how our body absorbs calcium (and other nutrients). Hormonal shifts may play a part for women, too.

Whatever the reason, lower bone density raises the risk of fracture or breakage—especially if we have an existing bone condition or have fractured a bone in the past.

If you’re concerned about bone health, discuss your concerns with your healthcare provider before using Semaglutide or Tirzepatide. They may suggest specific tests or prescribe calcium or Vitamin D supplementation.

How can I prevent muscle and bone density loss while taking a prescription weight loss medication?

Most health experts agree that engaging in activities that improve muscle, bone and cardiovascular health is important if you want safe, lasting change during medical weight loss.

Talk to your provider before any diet or exercise regimen. Or get even more personalized instruction from a licensed personal trainer, dietitian or nutrition coach.

Otherwise, these tips can get you started:

• Get regular exercise. Aim for 150-300 weekly minutes of moderate-intense aerobic activity or 75-150 minutes of vigorous-intense aerobic activity. (If you have an injury or disability, exercise as is safe and accessible for you.)
• Move your body in ways that you love! To get those minutes in, try a combination of dancing, martial arts, running, biking, walking, cycling, hiking or swimming.
• Prioritize resistance or weight training at least twice a week. Lifting small weights, using elastic bands, or trying push-ups, planks, or other bodyweight exercises can build muscle and improve bone density over time.
• Eat .5-.8 grams of protein per pound of your body weight every day from lean, quality protein sources—more if you’re actively exercising.
• Eat nutrient-dense, complex carbohydrates to encourage digestion and optimum health.
• Stay hydrated with water and other non-alcoholic beverages. These support digestion, which will help give your muscles and bones necessary nutrients!
• Before trying supplementation, ask your provider if calcium or Vitamin D supplements might benefit your muscle mass and bone density.

Can I get weight loss medication online?

Semaglutide and Tirzepatide are only prescribed by online weight loss doctors alongside exercise and diet modification. Fortunately, Dr. B offers several weight loss medications online via Shed It—our holistic prescription weight loss program!

Shed It combines affordable and effective prescription medications with streamlined support tools to help you shed pounds and negative habits. Our inclusive monthly fee covers all the essentials—no hidden fees or medication supply shortages here!

Start an online consultation to shed the habits holding you back so that you can meet a stronger, healthier you!

*Ozempic®, Wegovy®, Mounjaro® and Zepbound® are registered trademarks of their respective owners. Our use of these names is for informational purposes only and does not imply any affiliation, endorsement or approval by the trademark holders.

Sources:

Alabduljabbar, K., et al. (2022). The impact once-weekly Semaglutide 2.4 mg will have on clinical practice: A focus on the STEP trials. Nutrients.

Blum, D. (2023). The risks of taking drugs like Ozempic when you’re over 65. The New York Times.

Cava, E., et al. (2017). Preserving healthy muscle during weight loss. Advances in Nutrition.

Christoffersen, B. O., et al. (2022). Beyond appetite regulation: Targeting energy expenditure, fat oxidation, and lean mass preservation for sustainable weight loss. Obesity.

Hansen, M. S. (2024). Once-weekly Semaglutide versus placebo in adults with increased fracture risk: a randomised, double-blinded, two-centre, phase 2 trial. The Lancet.

Mayo Clinic. (2023). Strength training: Get stronger, leaner, healthier.

McCarthy, D., et al. (2021). Weight loss strategies and the risk of skeletal muscle mass loss. Nutrients.

Sargeant, J.A. (2019). A review of the effects of glucagon-like peptide-1 receptor agonists and sodium-glucose cotransporter 2 inhibitors on lean body mass in humans. Endocrinology and Metabolism.

US Department of Health and Human Services. (2018). Physical activity guidelines for Americans, 2nd edition.