By Katie Kirby, Pharmacist and Karen L. Kier, Pharmacist
ONU Healthwise Pharmacy

Roughly 12% of adults in the U.S. are using the injectable drugs known as GLP-1s. These medications include semaglutide (Ozempic) and tirzepatide (Mounjaro). With the use of these medications to help with weight loss and diabetes comes many questions about the long-term impact on health.  Although these medications have provided benefits, it is important to keep in mind the effect on the rest of the body to ensure optimal health.

Many studies have emerged about the impact of these medications on muscle mass, diet and nutrient deficiencies. A study in the American Journal of Clinical Nutrition focused on nutritional priorities relating to GLP-1 therapy. These researchers found the top nutritional priorities to support GLP-1 therapy included: utilizing a patient-centered approach, completion of baseline nutritional assessment and screening, management of gastrointestinal side effects, navigation of dietary preferences and intakes, prevention and mitigation of nutrient deficiencies, preservation of muscle and bone mass, maximization of weight reduction efficacy and promotion of other supportive lifestyle measures.

As noted by the researchers, muscle mass and nutrition are key. Another study, published in June 2025, specifically focused on the nutritional deficiencies and muscle loss seen in patients on GLP-1s. In this study, it was found that 12.7% of the over 4,000 patients enrolled had nutritional deficiency within 6 months of starting a GLP-1 and 22.4% within 12 months. One of the most common deficiencies identified was vitamin D and other common deficiencies included iron deficiency, dehydration, vitamin B deficiency and muscle loss. 

It is important to acknowledge that of all the deficiencies studied, there was a significant association between the discovery of a nutritional deficiency and visiting a dietician. Dietary counseling by a nutritionist may be beneficial for patients on these medications to better support nutritional monitoring and outcomes. It has previously been acknowledged by the Academy of Nutrition and Dietetics to maximize patient success rates, clinicians should be referring patients utilizing GLP-1 medications to a registered nutritionist. 

Muscle loss associated with GLP-1 therapy is another topic for researchers. Some recent studies have identified weight loss associated with GLP-1s may reduce lean body mass by as much as 20-50% in some patients. This occurred most frequently when patients are not utilizing lifestyle changes, specifically exercise-related changes, while utilizing these medications. 

A study published in Diabetes, Obesity, and Metabolism, focused on the changes in lean body mass associated with GLP-1 use and its management. They acknowledged with weight loss there is an expected reduction in muscle volume and it is important to conserve as much muscle mass as possible. One method commonly identified to help reduce muscle loss is to aim for a moderate increase in protein intake. A high protein diet has shown to help preserve muscle mass better than other dietary methods. This has been identified as being particularly important for patients utilizing GLP-1s as there is often a shift in food preferences including a decrease in the intake of protein.

Researchers have acknowledged exercise is another important strategy to help maintain muscle mass while experiencing weight loss. Both resistance and endurance exercises can help preserve muscle, but resistance training helps with improving muscle strength and building more muscle. Resistance training may include weight training, utilizing resistance bands, or body weight exercises. Each routine can be tailored to a specific patient's needs and capabilities.

Although research continues for anything related to the GLP-1 medications, it is important to look at what we already know. This includes utilizing an individualized approach and prioritizing nutrition and exercise to optimize health. A priority is to individualize protein intake goals, exercises, and nutritional goals. There has been an added benefit seen when utilizing a nutritionist throughout GLP-1 therapy. 

Never hesitate to ask your provider or pharmacist questions about your health and GLP-1 medications as your care should be specific to you!