Wegovy and other GLP-1 drugs have been called a breakthrough for weight loss, and in many ways, they are. They can quiet the endless appetite chatter, lower blood sugar, and help people finally see the scale move.
But here’s the part that’s often left out of the conversation: what kind of weight are you actually losing?
Because while the mirror might show less body fat, there’s another number that might quietly be falling too, your lean muscle mass. And that’s not a win for long-term health.
Weight loss isn’t the same as fat loss
The clinical trials on GLP-1 medications show impressive overall weight reductions, but when you look closer, as much as 30–40% of that “weight” can be lean tissue.
A sub-analysis of the STEP 1 and STEP 4 trials found that while total body weight dropped significantly, roughly a third of the loss came from fat-free mass (Kuk et al., 2023; Wharton et al., 2024).
That means muscle.
And muscle is not just about strength or tone, it’s your body’s metabolic engine, glucose sponge, joint protector, and one of the most powerful predictors of healthy ageing.
But here’s another biggie: when you eat less, and you will eat less on Wegovy, your micronutrient intake also drops. If you halve your food volume, you’re also likely cutting your vitamins, minerals, and phytonutrients by around half too.
That means even if you were previously eating “pretty well”, your nutrient status can start to slip fast. Iron, magnesium, calcium, vitamin D, B-vitamins, and essential fatty acids are all common casualties when calories fall.
So, as intake goes down, nutrient density needs to go up, think more colour, variety, and whole foods in smaller portions. It’s not about eating more, it’s about getting more out of less. Every mouthful counts when you’re in a calorie-restricted state.
This nutrient squeeze is just as critical as muscle loss, because it affects energy, recovery, mood, and immune health, all the stuff that makes weight loss sustainable rather than depleting.
Why losing muscle is a health risk
Let’s break down what happens if muscle loss goes unchecked during rapid weight loss:
- 🧠 Metabolism slows – Less muscle means your resting energy expenditure drops. You burn fewer calories doing the same things, which makes weight regain (often fat regain) more likely once medication stops (Rosenbaum & Leibel, 2010).
- 🩸 Blood sugar control weakens – Muscle tissue stores glucose and improves insulin sensitivity. Lose muscle, and your risk for insulin resistance, pre-diabetes, and Type 2 diabetes increases, ironically, the very conditions GLP-1s were designed to help (DeFronzo & Tripathy, 2009).
- 💪 Functional strength declines – Muscle loss translates to less stability, poorer balance, and greater injury risk. Everyday tasks — lifting shopping, climbing stairs, getting off the floor, can become noticeably harder.
- ❤️ Cardiovascular risk rises – Studies show lower muscle mass and strength are associated with higher rates of cardiovascular disease and mortality, even when accounting for body weight (Srikanthan et al., 2016).
- 🦴 Bone and joint health suffer – Muscle loading stimulates bone strength. With less mechanical stress, bone density can drop faster, raising the risk of fractures and osteoporosis (Scott et al., 2021).
- 🧬 Ageing accelerates – Sarcopenia (age-related muscle loss) is a known driver of frailty, loss of independence, and increased mortality. Losing muscle early just speeds up that trajectory (Cruz-Jentoft et al., 2019).
How to protect your muscle while using Wegovy
If you’re using a GLP-1 medication, you can absolutely keep (and even build) muscle, it just needs some attention and structure.
- Lift something heavy
Resistance training 2–3 times a week is non-negotiable. You don’t have to chase PBs, but you do need to give your muscles a reason to stay. - Eat enough protein
Aim for roughly 1.6–2.0 g per kg of body weight daily. Spread it across meals, and remember, appetite suppression can make this tricky, so prioritise protein first.
(Morton et al., 2018 found this range optimises muscle retention and growth during calorie restriction.) - Move every day
Don’t just sit still because the drug curbs hunger and fatigue. Walk, stretch, climb stairs, movement keeps muscle fibres engaged and metabolism humming. - Stay hydrated and monitor recovery
Lower food intake can affect electrolytes and energy. Hydration and rest help your body adapt safely to the lower-calorie state. - Work with someone qualified
Combining medical supervision with a health coach or PT ensures you’re not just “losing weight”, but improving your overall metabolic and functional health.
The bottom line
GLP-1 medications can absolutely be a valuable tool, especially for those who’ve struggled with traditional weight-loss methods. But they’re not a substitute for movement, nourishment, and strength.
If the scale drops but muscle mass, energy, and function drop too, the “success” can turn into a new set of health risks, slower metabolism, weaker bones, poorer glucose control, and faster ageing.
Fat loss alone isn’t the goal. Healthy, strong, functional weight loss is.
And that takes a plan, not just a prescription.
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