The "Muscle Tax" of Rapid Weight Loss
- The Review Course in Family Medicine
- 3 days ago
- 1 min read
Don't let your patient's muscles "ghost" them.
As the 2025 Canadian Family Physician article highlights, we must look beyond the scale.
Semaglutide averages 15% weight loss.
Tirzepatide averages 20% weight loss.
Lean mass loss is 24-40%.
Stop & Think: Before scrolling down, ask yourself: On a SAMP, what are the two mandatory lifestyle interventions you must pair with GLP-1 agonists to prevent sarcopenia?
We often celebrate a lower BMI, but rapid loss comes with a hidden cost to body composition. These new drugs are effective, but they can trigger significant loss of skeletal muscle and bone mineral density. This is especially risky in patients over 65 where "weight cycling" can actually increase mortality.
Indications:
Obesity (BMI over 30).
Overweight (BMI over 25) with weight-related comorbidities.
Long-term adherence is usually required.
Preservation:
Resistance Training: Effective at mitigating both muscle and bone loss.
Protein Supplementation: Necessary to sustain muscle mass during caloric deficits.
Aerobic Training: Beneficial for preventing weight-loss-related osteopenia.
The Risks: In elderly patients, the "obesity paradox" suggests that excess fat may actually be protective during illness. Inducing weight loss in this group can be harmful if it results in functional decline or fractures. If a patient stops these medications, they often regain weight as fat while the muscle remains "lost," leading to worse metabolic health than when they started.
EXAM TIP: On a SAMP, if you prescribe a GLP-1 agonist for weight loss, the "management" answer could be incomplete without specifying resistance training and protein intake. The College is testing your ability to prevent the complications of the treatment itself.
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