Ozempic is everywhere right now. In London alone, the number of people quietly taking semaglutide whether prescribed for type 2 diabetes, obesity, or obtained through private weight loss clinics, has grown dramatically over the past two years. And with that growth has come a wave of questions that personal trainers are now fielding in almost every consultation.
What does Ozempic actually do to your body? Can you still train effectively on it? What happens to your muscle mass? And perhaps most importantly if the drug is doing the heavy lifting on appetite and calorie intake, do you even need to exercise at all?
The answers matter more than most people realise. Here is what you need to know.
What Ozempic Actually Does
Semaglutide sold under the brand names Ozempic and Wegovy is a GLP-1 receptor agonist. It works primarily by mimicking a gut hormone that signals fullness to the brain, slowing gastric emptying and significantly reducing appetite. For most people, food simply becomes less interesting. Portions shrink naturally. Overall calorie intake drops often substantially without the conscious effort that traditional dieting requires.
The results can be dramatic. Clinical trials show average weight loss of 10 to 15 percent of body weight over 68 weeks in people taking semaglutide alongside lifestyle changes. For someone who has struggled with weight for years, that kind of result feels like a revelation.
But the number on the scale does not tell the whole story and this is exactly where exercise becomes not just helpful, but essential.
The Muscle Loss Problem
This is the conversation most weight loss clinics are not having with their patients, and it is the most important thing a personal trainer will tell you about Ozempic.
When the body loses weight through any mechanism it loses both fat and muscle. The ratio depends heavily on two factors: protein intake and resistance training. Without adequate protein and structured strength work, a significant proportion of the weight lost on semaglutide will be lean muscle mass rather than body fat.
Research on GLP-1 drugs suggests that in the absence of resistance training, somewhere between 25 and 40 percent of weight lost may come from lean tissue. For a person losing 15kg, that could mean 4 to 6kg of muscle gone alongside the fat.
The consequences are significant. Muscle mass is your primary driver of metabolic rate less muscle means a lower resting metabolism, which makes long-term weight maintenance considerably harder. It also means reduced strength, poorer posture, increased injury risk, and a body composition that looks and feels soft rather than lean and defined even at a lower weight. This phenomenon has been informally termed Ozempic body, and it is a direct result of weight loss without adequate training.
Why Exercise Is Non-Negotiable on Ozempic
If you are taking semaglutide and not exercising, you are not getting the best outcome available to you. You are losing weight but you are not transforming your body composition.
Structured resistance training while taking Ozempic does several things simultaneously. It signals to your body that muscle tissue needs to be preserved, not broken down. It builds and maintains the lean mass that keeps your metabolism running efficiently. It improves insulin sensitivity — which directly supports the metabolic improvements semaglutide is already driving. And it ensures that when you reach your goal weight, you arrive there with a body that looks strong and functions well — not simply a smaller version of where you started.
Two to three strength and conditioning sessions per week built around compound movements — squats, deadlifts, pressing, rows — is the minimum effective dose for muscle preservation during significant weight loss. This is not optional. It is the difference between a genuine body transformation and a number on the scale.
The Protein Challenge
Ozempic dramatically reduces appetite which sounds straightforwardly positive until you consider that most people on semaglutide are also significantly under-eating protein.
When overall food intake drops sharply, protein is often the first casualty. Smaller portions and reduced appetite mean that hitting 1.6 to 2.2g of protein per kilogram of bodyweight the range needed to support muscle preservation during a deficit becomes genuinely difficult for many people.
This is a serious problem. Without adequate protein, no amount of resistance training will fully protect your muscle mass during rapid weight loss.
Practical strategies that help: prioritise protein at every meal before eating anything else, use a quality protein supplement to top up intake when appetite makes whole food portions difficult, and choose protein-dense options when you do eat eggs, Greek yoghurt, chicken, fish, cottage cheese. You may not feel hungry, but your muscles still need feeding.
Training on Ozempic: What to Expect
If you are new to exercise and starting while on semaglutide, there are a few things worth knowing before your first session.
Energy levels may be lower than expected. Significantly reduced calorie intake affects energy availability for training. Do not expect to perform at the level you might on a standard diet. Reduce session intensity accordingly particularly in the first four to six weeks and build progressively as your body adapts.
Nausea can be a factor. Common in the early weeks of semaglutide use, nausea is often worsened by high-intensity exercise shortly after eating. Train on an empty stomach or at least two hours after a meal, and avoid very high-intensity work until gastrointestinal side effects settle.
Recovery takes longer. With lower calorie intake and potentially disrupted sleep in the adjustment period, your body has fewer resources for recovery between sessions. Prioritise sleep, keep training frequency sensible three sessions per week rather than five and do not mistake fatigue for laziness.
What Happens When You Stop Taking It
This is a question every person on semaglutide should be thinking about from day one, and very few are.
The clinical evidence is clear: the majority of people who stop taking semaglutide without having built sustainable lifestyle habits regain most of the weight within one to two years. The drug suppresses appetite — it does not teach you how to eat, how to train, or how to manage the behavioural patterns that contributed to weight gain in the first place.
The people who maintain their results after stopping are almost universally the ones who used their time on the drug to build genuine fitness foundations. Consistent strength training, sustainable nutrition habits, improved relationship with food, and a body with enough muscle to support a higher resting metabolism.
Ozempic is a tool. It is a powerful one. But it is not a replacement for the habits that produce lifelong results — and the window while you are on it is the best possible time to build them.
Should You Work With a Personal Trainer While on Ozempic?
If you are serious about getting the best possible outcome from semaglutide, working with a personal trainer in London is one of the most valuable investments you can make alongside it.
A good PT will build a resistance training programme that protects your muscle mass throughout the weight loss process, monitor your progress and adjust training as your body changes, help you navigate the energy and recovery challenges that come with reduced calorie intake, and build the fitness habits that ensure your results last long after the prescription ends.
The drug creates the calorie deficit. The training shapes what happens inside it.
Conclusion
Ozempic works. For many people it is a genuine turning point — finally getting traction on weight loss after years of struggle. But the outcome you get from semaglutide depends enormously on what you do alongside it.
Resistance training is not a bonus feature of your Ozempic journey. It is the mechanism by which you ensure the weight you lose is fat rather than muscle, arrive at your goal weight in genuinely good physical condition, and build the foundation that makes those results last.
If you are currently taking semaglutide — or considering it — and want a training programme built specifically around your situation, book a free consultation with Julian Ernst at Tempo Performance. We work with clients in Fitzrovia, across London, and worldwide online to ensure that whatever tools you are using, your results are built to last.