How do I avoid losing muscle while losing weight?
Updated: 5 days ago
The answer is simple:
Lift weights
Eat enough protein
Recover properly.
Getting those things right isn’t necessarily easy, but it is very achievable.
It's important to say up front: losing muscle during a fat-loss phase is something you should take seriously, particularly if the weight is coming off quickly.
And the reason to lift weights is not primarily to speed up your weight loss.
It is to help make sure the weight you lose comes from fat while you hold on to your muscle.
Why do you lose muscle when you lose weight?
Your body is constantly cycling, breaking down muscles and building them back up. What matters is the balance between the two.
When you are eating less than your body needs, protein is used as a fuel source.
If you lose more protein than you replace, your muscle mass gradually falls.
Strength training helps offset that by giving your body a signal to maintain it.
The protein you eat supplies the building materials
Recovery gives your body the opportunity to do the work.
This is why I programme muscle-building training for people who want to lose fat.
Even if we are not expecting much muscle growth, we still want the stimulus that helps preserve it.
What type of training should you do to keep your muscle?
Your strength training during fat loss is still just strength training and should look quite similar to the training that would be recommended if/when you are trying to build muscle. The only real difference is what/how much you eat.
Do not replace proper lifting with lighter weights and circuits because you are now trying to get leaner.
By proper lifting, I mean a session centred around compound moves like squats, lunges, pressing and pulling exercises. I mean choosing weights that are tough for anything between, say, 5 and 15 reps.
And then adequate rest breaks (1-3 minutes) so you can hit each set with the required intensity.
How often should you lift weights?
For someone new to training, I would usually begin with two full-body sessions a week.
That means each muscle is going to get that supportive growth signal twice per week.
More good-quality training can help, provided you can recover from it.
But more is not always better. If your food intake is lower and recovery is becoming difficult, adding more sessions can make the problem worse.
Add to that, the more you do the less valuable each individual session becomes, training 10x a week doesn't progress you 10x faster than one session.
How hard should you push yourself?
This is an important question, and the answer is: Hard. The working sets need to be challenging.
The repetitions towards the end of a demanding set are what provide the strongest stimulus to maintain or build muscle.
If you stop as soon as an exercise becomes uncomfortable, you are stopping before you have done the most useful work.
Keep good technique, but don’t confuse a slower, harder final rep with a bad rep.
That's where an experienced eye keeping watch over your training can make the biggest difference.
Should you still expect to get stronger?
You should still be trying to improve, but you may find that you don't make a huge amount of strength progress.
It all depends on how experienced you are.
A newbie will get stronger in spite of rapid fat loss, and someone who's been lifting for a decade is probably not going to make any progress at all.
But you should always be pushing to improve.
That might mean another repetition, a little more weight, better control or a greater range of movement. There should be a purpose to the session.
Also, getting stronger does not always require bigger muscles. You can improve your strength by becoming better at using the muscle you have.
Strength gains do not prove that you have lost no muscle, but they are a useful sign that your training is doing something worthwhile.
How much protein should you eat?
Do not let your protein intake fall simply because you are eating less overall.
As a practical portion guide, aim for 4–5 palm-sized portions of protein-dense food per day. If you prefer to measure your intake, aim for 1 gram of protein per pound of desired body weight.
Those are the points at which you've maxed out the benefits, so even getting yourself closer to those numbers will be a big benefit.
How to do that?
My order is simple:
At the very least, have a protein-rich food at every main meal.
Better still, make it a decent portion, roughly a palm-sized serving as a starting point.
Even better, spread those servings across the day.
Finally, consider whether measuring your intake would help, and aim for 1 gram of protein per pound of desired body weight.
Prioritising is critical.
If breakfast and lunch barely contain any protein, sort that out before worrying about the exact timing of your shake.
What should you do if you feel too tired to train?
First, work out why you are tired.
If you are losing weight quickly, or you are already fairly lean, the energy deficit may be making recovery harder.
In that situation, I would consider reducing the amount of training, potentially including the number of sessions, while protecting the quality of the work you keep.
Do fewer things well.
If your weight loss is gradual and you have plenty of body fat to lose, I would look closely at your sleep, workload and daily routine rather than immediately blaming the diet.
How can you tell if you are losing muscle?
It's difficult.
Getting weaker over time is one warning sign, although it is not proof on its own.
What's difficult is that you may not notice muscle loss immediately.
Spread across your whole body, a meaningful loss can be hard to spot in the mirror. That is why I would take steps to prevent it rather than wait until it becomes obvious.
Track your training alongside your weight. Photos, measurements and how your clothes fit can add context.
If your waist is getting smaller and your training is holding up, that is more encouraging than weight loss accompanied by steadily declining performance.
I would not put much faith in individual muscle or body-fat readings from bathroom scales. They are sensitive to hydration and measurement conditions.
Even consistent readings need interpreting carefully.
Muscle is not the only tissue worth protecting. Bone health matters too, particularly for women around and after menopause. A falling number on the scales does not tell you the whole story about your health.
Is the advice different if you are taking Mounjaro?
The main training principles are the same.
You still need to challenge your muscles, eat enough protein and recover. Taking Mounjaro does not require a completely different set of exercises.
If you are taking Mounjaro and deciding how to exercise, read What is the best exercise to do on Mounjaro?.
What may change is your appetite and the speed at which you lose weight.
Eating less can become easier, but that does not mean you can ignore what your remaining meals contain.
You still need to nourish yourself and support your training.
If you cannot eat adequately or side effects are interfering with everyday life, speak to your prescriber. Medication decisions belong with them.
I would start strength training while you are losing weight rather than wait until you finish. Protect the muscle you have and give yourself something to achieve beyond becoming lighter.
If you have already lost substantial weight and are unsure what comes next, read Lost Weight on Mounjaro and Still Unhappy With Your Body?
If you want help with your training, I offer personal training in Kentish Town.
We can review your programme, technique and progress, then make sure your time in the gym is doing the job you need it to do.
