Weight loss drugs, such as those containing GLP-1 agonists like Wegovy and Mounjaro, have emerged as effective tools for people struggling to lose weight. These drugs reduce appetite and sometimes slow digestion which can help people to consume fewer calories.
Author
- Jack McNamara
Senior Lecturer in Clinical Exercise Physiology, University of East London
But while these drugs can significantly lower body weight , it's important you take steps to avoid losing too much lean mass while taking them.
When we lose fat, it often unfortunately comes with a hidden cost: losing lean mass. Lean mass is made up of your muscles, bones and organs - essentially everything in your body that isn't fat. Preserving as much of this lean mass as possible is vital for staying strong, keeping a healthy metabolism and enjoying a better quality of life.
But why does losing lean mass happen in the first place? When we lose weight the body sometimes taps into muscle as a source of energy. Research shows that 20-30% of weight lost during a diet comes from muscle rather than fat alone. This is especially true if protein intake or physical activity isn't sufficient .
Loss of muscle matters for several reasons. First, muscle burns more calories than fat, even when you're not doing anything. Maintaining muscle mass supports a healthier metabolism that can help you maintain your weight loss long term.
Second, muscle is important for many everyday tasks - from lifting shopping bags to climbing stairs.
Preserving muscle can also keep you feeling more energetic and reduce the likelihood of regaining weight later .
Thankfully, resistance training (also known as strength training) has been consistently shown to help reduce muscle loss when losing weight. This holds true whether you switch to a healthier diet or use weight loss drugs as part of your strategy.
Even though specific studies looking at GLP-1 agonist drugs combined with exercise are still limited, early evidence suggests that people who regularly do resistance workouts tend to retain more muscle than those relying purely on the drug or diet changes.
Why resistance training works
When you challenge your muscles against resistance - whether that's weights, resistance bands or just your own body weight - you signal the body to preserve that valuable muscle tissue . Your body responds by strengthening the muscles involved during these exercises so they can handle that challenge again.
If you're in a calorie deficit - either from dieting or while taking a weight loss drug - these exercises help direct your body to burn more fat instead and hang on to muscle . There's also a beneficial metabolic effect: muscle tissue burns more calories at rest than fat, which can support long-term weight management .
Even short sessions of resistance training a few times a week can help. One study found that resistance training for as little as 11 minutes per session, three times a week was enough to elicit changes.
You don't even need a gym membership or fancy machines. Bodyweight exercises such as push-ups, lunges and planks are a great place to start. Add simple items like water bottles or backpacks filled with books for extra resistance. Over time, you can consider using resistance bands or free weights (such as dumbbells) to challenge your muscles as you get stronger continuously.
Also, consider adding moderate cardio activities such as brisk walking, cycling or swimming. Cardio helps burn additional calories, benefits heart health and nicely complements resistance training enhancing reductions in body fat.
Keeping active
Some people worry about feeling too tired or lightheaded to exercise while on weight loss drugs. Monitoring how your body responds is essential, especially at the beginning. You might find it easier to break workouts into short sessions, such as 10 to 15 minutes of strength training, two or three times a day. This approach can be less intimidating and can fit into a busy schedule.
Some other things you can do when starting resistance training include:
- Start slow: If you've never lifted weights or done formal exercise before, try simple bodyweight moves first. Squats, push-ups (on your knees if needed) and planks are good starting exercises.
- Use resistance bands: These are affordable, portable and offer varying difficulty levels. Using bands, you can perform exercises such as biceps curls, shoulder presses and glute bridges. Resistance bands can provide a safer, more accessible and versatile way to build a foundation for those new to weight training.
- Focus on major muscle groups: Aim to work your legs, back, chest, shoulders arms and core. Focusing on major muscle groups improves functionality for daily activities, supports weight loss and reduces injury risk by strengthening large, stabilising muscles.
- Mind your form: Good technique is crucial to avoid injury. Move slowly and with control, especially when adding weight or increasing resistance.
- Track progress: Whether it's increasing the number of reps, adding heavier weights or improving balance, keep note of your achievements. Progress can be a great motivator.
Taking weight loss drugs can be a gamechanger for people who have struggled to lose weight. But medication alone won't necessarily protect your muscle mass or overall strength. Resistance training helps ensure muscle isn't sacrificed as fat is lost. It also supports a healthy metabolism and can improve energy levels, making daily activities more manageable and more enjoyable.
Combining weight loss drugs with a balanced diet, regular resistance workouts and some cardio makes you far more likely to preserve the lean mass that helps keep your body strong and functional. This balanced approach isn't just about the number on the scale - it's about feeling capable, staying healthy, and setting yourself up for long-term success.
Jack McNamara does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
