The Weight You Don’t Want to Lose: Why Muscle Matters in Fat Loss (and the Hidden GLP-1 Epidemic)

How to Know You’re Burning Fat (Not Muscle) & Why This Matters !

You’re doing the work: training, eating well, watching the scale. But how do you know if what you’re losing is fat and not the muscle that keeps your body strong, toned, and metabolically active? This is a big concern, especially as large number of people are prescribed GLP-1's to assist them in achieving their goal weight.

The rise of GLP-1 medications

There’s a growing trend toward using GLP-1 medications such as Mounjaro, Ozempic, and Wegovy for weight loss. Some analysts have projected that GLP-1 prescriptions (for all approved uses) could reach 40% penetration by 2030 (around 2.4 million people) if trends continue - though this figure includes all indications, not solely weight-loss use.

These medications can be effective tools for appetite control and metabolic reset - but ONLY when used correctly. My fear is that without long term changes to habits in nutrition, activity, and resistance training, these drugs can lead to muscle loss and metabolic slowdown. Long term those individuals who are not using the medications properly and chasing insane levels of suppression will be left with worrying side effects as well as fatigue, lower energy expenditure, and difficulty maintaining their results. One concern I have is ensuring my clients are strong and HEALTHY into their later years, so by all means use these tools but read the manufacturers guidance, engage a professional dietician or PT to help you on your journey and prioritise your long term health and wellness.

The scans below show two thighs: one with healthy muscle, one with muscle loss (sarcopenia). The darker grey area represents muscle - notice how much less there is on the right? That’s what can happens with age, or when crash dieting, starving, or relying on GLP-1s without enough protein and strength training.

While GLP-1 medications are effective for weight loss, emerging research indicates they may increase the risk of lean mass loss, particularly in women or older adults who don’t prioritise protein intake and resistance training. A 2025 review highlighted that in populations already predisposed to sarcopenia, GLP-1s could accelerate muscle decline and frailty if protective strategies aren’t used. (Memel, Z., Gold, S. L., Pearlman, M., Muratore, A., & Martindale, R. (2025). Impact of GLP-1 receptor agonist therapy in patients high risk for sarcopenia. Current Nutrition Reports, 14, Article 63. https://doi.org/10.1007/s13668-025-00649-w)

GLP-1s are a tool - not a long-term solution

To use them safely and effectively, they should be paired with:

✅ Adequate nutrition (this isn't chasing the highest level of suppression to starve yourself to a smaller body), think whole foods, lean proteins, not just less processed foods.

✅ Sufficient protein intake to maintain and build lean muscle mass

✅ Regular and adequate resistance training (Don't know how? Engage a professional!)

✅ Slow, steady fat loss

Employ smart strategies to avoid your body using muscle for energy - this only make the journey arduous - resulting in fatigue, and in the longer term a slower metabolism, hair loss, and a harder time maintaining hard earned results.

🔍 Clues that Indicate You’re on the Right Track: Burning Fat, Not Muscle

1️⃣ Your strength is holding steady or improving.

If you can lift the same or heavier weights each week, you’re preserving muscle. Strength loss = a red flag for muscle loss.

2️⃣ Your energy levels stay consistent.

Proper fat loss shouldn’t leave you exhausted by mid-afternoon. If you’re constantly tired, you may be under-fuelled and/or under-recovering.

3️⃣ You’re eating enough protein.

Aim for 1.6–2.2 g of protein per kg of bodyweight daily. Protein is the key to maintaining lean tissue while in a calorie deficit.

4️⃣ Your weight loss is slow and steady .

Sustainable fat loss happens at about 0.5–1 kg per week. Faster drops often mean you’re losing muscle, water, or glycogen. Gradual progress protects lean tissue and performance.

5️⃣ You’re not losing hair or noticing skin/nail changes.

Rapid weight loss or low-protein diets can cause hair thinning, brittle nails, and dull skin - all signs of inadequate nutrition.

6️⃣ You’re resistance training consistently

At least 2–3 strength sessions per week helps signal your body to keep muscle while using fat for fuel.

7️⃣ You’re recovering well

Poor sleep, dehydration, and chronic stress elevate cortisol, which accelerates muscle loss. Prioritise recovery, rest, and stress management.

📊 Pro Tip: Measure What Actually Matters !

A DEXA scan or Evolt body composition scan gives a far clearer picture than the scale.

In particular try to track % :

• Lean muscle mass

• Body fat percentage

• Visceral fat

These metrics show your true progress - and help you keep muscle while losing fat. Also remember that weight loss is never linear, you can gain 1kg easily and this can be due to hormones, water, glycogen stores, don't stress and diet harder - just be consistent. Think of your weight loss journey as a journey to change the habits that may have got you here in the first place, not a race.

💪 The Bottom Line

The goal isn’t just to lose weight: it’s to lose fat and keep that beautiful metabolically active muscle.

That’s how we build:

✅ A strong metabolism

✅ A powerful, capable body

✅ Results that last long after the script or diet ends

At DTD we train for our future selves, not just for smaller numbers on the scale.Interested in resistance training with me? I am taking a limited number of online and hybrid coaching clients, DM me for more information.

Chantal x

Disclaimer: The information shared in this article reflects general health and fitness knowledge and publicly available research, including studies such as Memel et al., 2025, Current Nutrition Reports. It does not constitute personalised medical or nutritional advice. Readers using GLP-1 medications or with pre-existing health conditions should consult their healthcare provider for tailored guidance.