SEMAGLUTIDE

A Canadian physician, Peter Attia, claimed on an Instagram post that "almost every patient we put on this drug [semaglutide] has lost muscle mass at a rate that alarms me."

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So what does the medical literature say about diet and weight loss as it pertains to muscle mass?

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1) It is well established that up to 30% of total weight loss in obese individuals will be from lean body mass.1 The amount of lean body mass lost will be higher in short term and crash diets.2. Normal weight individuals will lose upwards of 35% of lean body mass during weight loss.3

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2) In general, "compared with persons with normal weight, those with obesity have more muscle mass but poor muscle quality; [additionally,] diet-induced weight loss reduces muscle mass without adversely affecting muscle strength"4

 

 3) The following quotations come from four different studies evaluating the effect of semaglutide on lean body mass during weight loss.  All four concluded that semaglutide did in fact result in loss of lean body mass (as would be expected), but overall it improved the ratio of lean body mass to fat mass.

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a. "In adults with overweight/obesity, once-weekly semaglutide 2.4 mg was associated with reduced total fat mass and regional visceral fat mass, and a relatively increased proportion of lean body mass. Greater weight loss was associated with greater improvement in body composition (total lean body mass to total fat mass ratio).”5

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b. “Visceral Adipose Tissue (VAT) decreased, while Fat Free Mass and Skeletal Muscle Mass (SMM) were preserved during therapy, resulting in a beneficial increase in the SMM/VAT ratio.  Finally, an overall improvement in body fluid distribution was observed.”6

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c.  "In a real-world setting, semaglutide can reduce the weight and fat of obese patients while effectively maintaining muscle mass and muscle strength."7

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d. “The 24-week treatment with oral semaglutide ameliorated glycemic control with reduction of body fat but not muscle mass in Japanese patients with type 2 diabetes.”8

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4) Semaglutide has been shown to reduce the incidence of death from cardiovascular causes, nonfatal myocardial infarction, and nonfatal stroke in both diabetic and non-diabetic patients.9  Therefore, the risk of loss of muscle mass must be weighed against the benefit of improved cardiovascular and cerebrovascular health. 

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5) "Both endurance- and resistance-type exercise help preserve muscle mass during weight loss, and resistance-type exercise also improves muscle strength."10

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Conclusion:  You can expect to lose both lean body mass and fat mass during a diet assisted with semaglutide.  According to peer reviewed medical research, you can expect to see an improvement in your overall ratio of lean body mass to fat mass.  Best practice suggests that you accompany weight loss with some type of endurance or resistance exercise to minimize the effects of the loss of lean body mass during any weight loss program. ​​​​​​​​​​​​​​​​