Losing Weight on a GLP-1? Why Protecting Your Muscle Matters

Why people are asking now

GLP-1 based medicines, including tirzepatide (Mounjaro) and semaglutide (Wegovy), have changed how weight management is approached in the UAE. Obesity rates here have historically sat above the global average, and a recent report in The National quotes a senior UAE physician saying the medicine may provide only part of the solution, with lifestyle accounting for the rest.

As more people use these medicines, a new question comes up in consultations: “I’m losing weight, but am I losing muscle too?” It is a fair question, and the honest answer is nuanced.

What GLP-1 weight management is

GLP-1 receptor agonists, and dual agonists such as tirzepatide, act on appetite and fullness signals. Many people eat less as a result. In supervised care, the medicine sits alongside nutrition, activity, sleep and regular follow-up. It is a prescription treatment, so it needs a medical assessment before it starts.

How body composition changes during weight loss

Whenever someone loses a significant amount of weight, by any method, the body loses fat mass and some lean mass. Lean mass is not the same as muscle. It also includes water, organs, connective tissue and bone mineral. That distinction matters when reading headlines about “muscle loss”.

What the evidence actually says

A DXA body-composition substudy of the SURMOUNT-1 trial (Look et al., 2025) scanned 160 participants at baseline and at week 72. In the tirzepatide group, body weight fell by about 21.3%, fat mass by about 33.9% and lean mass by about 10.9%. Roughly 75% of the weight lost was fat mass and about 25% was lean mass. The authors report that this split was similar in the placebo group, which lost far less weight overall.

What this suggests: most of the weight lost was fat, and the proportion of lean mass lost was in the range commonly seen with substantial weight loss in general. The lean mass lost in absolute terms is still real, which is why supportive habits are recommended.

The honest limits:

• This is a substudy of 160 people, analysed after the main trial, so it should be read with caution.
• DXA measures lean mass, not muscle strength or function.
• Findings may not apply equally to every age, sex, ethnicity or starting weight.
• Trial participants receive structured support that may differ from everyday practice.
• Research is ongoing and recommendations may change.

What professional bodies recommend

A 2025 joint advisory from the American Society for Nutrition, the American College of Lifestyle Medicine, the Obesity Medicine Association and The Obesity Society recommends supporting people on GLP-1 therapy with adequate protein and resistance training to help preserve muscle. It also highlights monitoring for nutrient shortfalls (such as fibre, calcium, iron and magnesium), managing gastrointestinal side effects, and starting treatment with a personalised baseline assessment. The summary I opened did not give specific protein amounts or training schedules, so targets should be set individually by your physician or dietitian.

Who may benefit from supervised GLP-1 care

Medical weight management may be considered for adults with obesity, or with overweight and weight-related health conditions, after an assessment. Suitability depends on your history, medicines, goals and prior attempts. Many people also come in at a weight plateau and want to understand what else could help.

What happens in a consultation

A typical visit may include:

• A medical history, medicines review and weight and measurement baseline.
• Discussion of goals, eating patterns, sleep, stress and activity.
• Blood tests where appropriate.
• A decision on whether medication is suitable, and which one, within the approved options available in the UAE.
• A plan for protein, strength-based activity and follow-up.

Realistic results and timeline

Weight loss with these medicines is gradual, and in trials it was assessed over many months. Results vary widely between individuals. No outcome is guaranteed, and some people lose less than the trial averages. Dose is usually increased step by step, and follow-up is how the plan is adjusted.

Supportive habits that physicians commonly discuss

• Protein: adequate daily intake, spread across meals, with a target agreed with your clinician or dietitian, especially if your appetite is low.
• Resistance training: regular strength work, built up safely for your fitness and joints.
• Hydration, fibre and micronutrients: appetite suppression can reduce intake of these.
• Sleep and stress: both influence appetite and recovery.
• Regular review: body composition, blood tests and side effects tracked over time.

Side effects and safety

Common side effects include nausea, vomiting, diarrhoea, constipation and reduced appetite. These often ease but can be significant. Less common but serious risks, including gallbladder problems and pancreatitis, are described in the product information, and your physician will review these with you. Reduced eating can lead to low protein or nutrient intake, which is one reason follow-up matters. Report persistent vomiting, severe abdominal pain or any symptom that worries you.

Who should avoid it or take extra care

These medicines are not suitable for everyone. Extra caution or avoidance may apply with a personal or family history of certain thyroid tumours, a history of pancreatitis, pregnancy or planned pregnancy, breastfeeding, some gastrointestinal conditions, and certain medicine combinations. Anyone with a history of disordered eating needs careful assessment. Your physician will review this before prescribing.

How it compares with other approaches

Lifestyle-only programmes work for many people and carry no medicine risks, though results may plateau. Bariatric surgery can produce larger weight loss for suitable candidates but involves surgical risks. GLP-1 care sits between them: non-surgical, prescription-based and dependent on ongoing habits. Stopping medicine may lead to regain in some people, so a maintenance plan is part of the discussion from the start.

A note on regulation: only use products that are licensed and approved in the UAE, supplied through a licensed pharmacy on prescription. Be cautious of “research peptides”, imported pens or unregulated online sellers, which may be counterfeit or unsafe.

Questions to ask before booking

1. Is this medicine approved and licensed in the UAE, and who supplies it?
2. What assessment and blood tests will I have first?
3. How will my muscle and body composition be monitored, not just the scale?
4. What protein and strength plan do you suggest for me?
5. What are the side effects and when should I call?
6. What is the plan if I stop, plateau or cannot tolerate it?

FAQs

Will I definitely lose muscle on a GLP-1?
Some lean mass is lost with most substantial weight loss. In the SURMOUNT-1 DXA substudy, about a quarter of the weight lost was lean mass. Individual results vary.

Is lean mass the same as muscle?
No. Lean mass includes water, organs and other tissues as well as muscle.

Can protein and strength training prevent muscle loss entirely?
They are recommended to help preserve muscle, but no approach is guaranteed to prevent all loss.

Do I need to exercise while on the medicine?
Professional advisories recommend resistance training alongside it. Your physician can advise what is safe for you.

Will I regain weight if I stop?
Some people do, which is why a long-term plan is discussed early.

Are unapproved peptides a substitute?
No. Unapproved or unlicensed products should be avoided.

Book a consultation

If you would like to discuss whether supervised weight management is suitable for you, you can book a consultation with Dr. Pravin Kumar in Dubai.

Sources

• Look M, et al. Body composition changes during weight reduction with tirzepatide in the SURMOUNT-1 study of adults with obesity or overweight. 2025 (abstract record, DOI 10.1111/dom.16275)
• Nutritional priorities to support GLP-1 therapy for obesity: a joint advisory (ASN, ACLM, OMA, TOS), as summarised by Medical Dialogues
• The National: Weight-loss medicine must be paired with lifestyle changes, UAE obesity expert says (27 Aug 2026)

Disclaimer: This article is educational information, not medical advice. Results vary, and suitability is confirmed only after an individual assessment.