While GLP-receptor agonist drugs like Wegovy, Ozempic, and Zepbound have taken the weight loss industry by storm, experts in metabolism caution that fat isn’t the only thing being lost.

Two professors from the Pennington Biomedical Research Center, Dr. Steven Heymsfield, professor of metabolism and body composition, and Dr. M. Cristina Gonzalez, adjunct and visiting professor in metabolism–body composition, along with colleagues Dr. Carla Prado of the University of Alberta and Dr. Stuart Phillips of McMaster University, have brought concerns to light about significant muscle loss in their recent commentary, "Muscle Matters: The Effects of Medically Induced Weight Loss on Skeletal Muscle," published in The Lancet.

The authors note that decreases in fat-free mass represent muscle loss, which may account for 25 to 39 percent of all weight loss between 26 to 72 weeks. This rate of muscle loss is much higher than what would typically be seen with non-drug calorie restriction or the normal aging processes and could result in unintentional negative health consequences.

While there are metabolic benefits of GLP-1 receptor agonists, possible adverse effects of muscle loss should not be ignored. Skeletal muscle is necessary for physical strength and function but is also important for metabolic health and regulation of the immune system.

A drop in muscle mass has been associated with decreased immunity, elevated infection risk, poor blood sugar regulation, and other health risks. The authors advise that muscle loss related to weight reduction may exacerbate conditions such as sarcopenic obesity, which is common in those with obesity and adds to poorer health outcomes such as cardiovascular disease and increased rates of mortality.

It’s unclear what the short-term effects of muscle loss on physical strength and function are. The commentary underscores the need for future research to examine how loss of muscle mass might improve muscle composition and quality. The authors encourage the need for a multisystem approach to weight loss treatment, using GLP-1 receptor agonists with exercise and nutritional therapies to preserve muscle mass.

Dr. Heymsfield said, "We have to be mindful of the side effects that we are seeing with the new weight loss medications, such as a person eating less while on the medications and not getting the appropriate amount of dietary vitamins and minerals. Also, when a person loses weight, they are not only losing fat, they also lose muscle. We are looking at how that muscle loss can be better managed with consumption of an adequate amount of protein along with an optimum amount of exercise."

This continued conversation reinforces the importance of ensuring that weight loss treatments support total health, including muscle maintenance, as part of an overall strategy for treating obesity. 1

To help your clients maintain muscle while using GLP-1 receptor agonist drugs:

·         Stay abreast of current research on the safety of weight loss medications.

·         Ensure clients are working with an RD during their weight loss journey.

·         Obtain a baseline of fat mass and fat-free mass before starting medication if possible.

·         Educate clients about the potential side effects of GLP-1 receptor antagonists.

·         Advise clients about both adequate calorie and protein intake during weight loss.

·         Provide meal and snack ideas that contain adequate protein.

·         Encourage strength training exercises. Refer clients to a physical therapist or personal trainer for advice.

·         Monitor clients for signs or symptoms of eating disorders, which could be problematic in this population. 2

References:

1. Carla M Prado, Stuart M Phillips, M Cristina Gonzalez, Steven B Heymsfield. Muscle matters: the effects of medically induced weight loss on skeletal muscle. The Lancet Diabetes & Endocrinology, 2024; 12 (11): 785 DOI: 10.1016/S2213-8587(24)00272-9

2. Guerdjikova AI, Ward A, Ontiveros M, McElroy SL. Semaglutide Misuse in Atypical Anorexia Nervosa-A Case Report. J Clin Psychopharmacol. 2024 Mar-Apr 01;44(2):179-180. doi: 10.1097/JCP.0000000000001820. Epub 2024 Feb 7. PMID: 38329147.