GLP-1 Muscle Loss Risk Assessment
Evaluate your risk of lean muscle loss on Ozempic, Wegovy, or Mounjaro and get a personalized protection plan
Your Muscle Loss Risk Assessment
Understanding Muscle Loss on GLP-1 Medications
GLP-1 receptor agonists such as semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound) have transformed obesity treatment, but they come with a significant side effect that many patients overlook: muscle loss. Data from the landmark STEP clinical trials revealed that 39-40% of the weight lost on semaglutide was lean body mass -- not fat. This means that for every 10 pounds lost, approximately 4 pounds may come from muscle, bone, and other non-fat tissues. Without deliberate intervention through adequate protein intake and resistance exercise, patients risk losing the very tissue that supports their metabolism, mobility, and long-term health outcomes.
The range of lean mass loss on GLP-1 medications is wide, spanning from as low as 15% to as high as 60% of total weight lost, depending almost entirely on individual behavior. The two most powerful modifiable factors are protein intake and resistance training. Research published between 2024 and 2026 consistently demonstrates that consuming 1.2 to 1.6 grams of protein per kilogram of body weight per day -- roughly double the standard RDA of 0.8g/kg -- can significantly reduce muscle wasting during rapid weight loss. When this elevated protein intake is combined with structured resistance training at least twice per week, lean mass loss can be reduced to below 20% of total weight lost, preserving metabolic rate and physical function.
Several risk factors amplify the danger of muscle loss on GLP-1 therapy. Age is a major contributor: adults over 65 already experience age-related sarcopenia (muscle decline of 3-8% per decade after age 30), and adding medication-induced caloric restriction accelerates this process. Longer medication duration also increases cumulative lean mass loss, as the body has more time in a catabolic state. Patients who combine low protein intake with zero resistance training represent the highest-risk group, facing potential lean mass losses of 40-60% of total weight lost. This pattern is especially common in patients who rely solely on the appetite-suppressing effect of GLP-1 drugs without making complementary lifestyle changes.
The good news is that muscle loss on GLP-1 medications is largely preventable. Evidence-based protection strategies include consuming at least 1.2-1.6g of protein per kilogram of body weight daily (distributed across 3-4 meals), performing progressive resistance training 2-4 times per week, and ensuring adequate sleep and recovery. Patients should discuss their muscle preservation strategy with their prescribing physician and ideally work with a registered dietitian and certified trainer. This risk assessment tool helps you identify your current vulnerability level and provides a personalized action plan to protect your lean mass while maximizing fat loss on GLP-1 therapy.
How to Use This Risk Assessment
- Enter your current daily protein intake in grams. If you are unsure, track your meals for a few days using a food diary or app to get an accurate estimate.
- Select how many days per week you exercise from the dropdown, and check the boxes indicating whether you do resistance training, cardio, or both.
- Enter your age and current body weight in kilograms. These factors significantly influence your baseline risk for muscle loss.
- Enter the total number of weeks you have been on your GLP-1 medication. Longer durations increase cumulative exposure to lean mass loss.
- Click "Assess My Risk" to receive your risk score (0-100), estimated lean mass loss percentage, protection score, factor breakdown, scenario comparison, and a personalized action plan tailored to your specific risk profile.
Frequently Asked Questions
How much muscle do people actually lose on GLP-1 medications?
Clinical data from the STEP trials show that approximately 39-40% of weight lost on semaglutide (Ozempic/Wegovy) is lean body mass when patients do not actively intervene with high protein intake and resistance training. The actual range is 15-60% depending on individual factors. With proper protein intake (1.2-1.6g/kg/day) and resistance training at least twice per week, lean mass loss can be reduced to below 20% of total weight lost.
What protein intake level reduces muscle loss risk on GLP-1 drugs?
Current clinical evidence recommends a minimum of 1.2 grams of protein per kilogram of body weight per day for GLP-1 users, with 1.4-1.6g/kg being optimal for most patients. Those who include regular resistance training may benefit from even higher intakes up to 2.0g/kg. For context, the standard RDA of 0.8g/kg is insufficient during rapid medication-induced weight loss. For a 90kg person, this means consuming at least 108-144g of protein daily, spread across multiple meals.
Does age affect muscle loss risk on Ozempic or Mounjaro?
Yes, significantly. Adults over 65 are at elevated risk because they already experience age-related sarcopenia -- a natural decline in muscle mass of 3-8% per decade starting around age 30. When GLP-1 medication-induced caloric restriction is layered on top of this existing muscle decline, the combined effect can be substantial. Older adults on GLP-1 therapy should prioritize resistance training and protein intake even more aggressively than younger patients, and should discuss muscle preservation strategies with their healthcare provider.
Is resistance training or cardio better for preventing muscle loss?
Resistance training (weight lifting, bodyweight exercises, resistance bands) is significantly more effective than cardio for preserving lean muscle mass during weight loss. While cardio burns calories and improves cardiovascular health, it does not provide the mechanical stimulus needed to signal your muscles to maintain or grow. Studies show that patients who perform resistance training 2-4 times per week retain substantially more muscle compared to those who only do cardio or no exercise at all. Ideally, combine both types for optimal health, but prioritize resistance training if you must choose one.
How does medication duration affect muscle loss?
Longer time on GLP-1 medication increases cumulative lean mass loss because the body spends more time in a caloric deficit. During the first 12-16 weeks, weight loss is typically fastest and the ratio of muscle-to-fat loss can be highest, especially during dose escalation. After 6 months, the rate of weight loss typically slows as the body adapts, but some muscle loss continues. Patients on GLP-1 therapy for over 6 months should be especially vigilant about their protein intake and resistance training routine to counteract cumulative effects.
Can I regain muscle lost during GLP-1 treatment?
Yes, muscle can be rebuilt after GLP-1 treatment, but it is significantly harder and slower to regain muscle than it is to lose it. Rebuilding lost muscle requires a dedicated resistance training program, adequate protein intake (1.6-2.2g/kg/day), and often a caloric surplus or at least maintenance-level eating -- which runs counter to continued weight management goals. Prevention is far more effective than rehabilitation, which is why assessing your risk and implementing protective strategies from the start of GLP-1 therapy is critical.
What is a good Protection Score in this assessment?
A Protection Score of 70% or above indicates that your current protein intake, exercise habits, and other factors provide strong defense against excessive lean mass loss. Scores between 40-69% suggest moderate protection with room for improvement -- typically in either protein intake or resistance training frequency. Scores below 40% indicate significant vulnerability, meaning you are likely to lose a high proportion of lean mass relative to fat during your weight loss. The action plan provided with your results gives specific, prioritized steps to improve your score.
