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TL;DR: to lose weight without losing muscle, combine a moderate deficit (about 300-500 kcal below what you burn, 0.5 to 1 kg a week), protein at 1.6-2.2 g per kilo, strength training 2 to 4 days a week and 7-9 hours of sleep. Very low-calorie diets and rushing cost muscle and set up rebound weight gain. With an eating disorder, pregnancy or diabetes on medication, see a health professional.
Losing weight without taking muscle with it is what nearly everyone wants, and what is hardest when you are in a hurry. Here is how to set the deficit, how much protein you need, what strength training does and how to keep the weight off.
Do you lose muscle when you lose weight?
Do you lose muscle mass when you lose weight?
Some, yes, above all if the deficit is large, the diet is low in protein or there is no strength training. The weight that drops on the scales is a mix of fat, water and some lean mass. With a moderate deficit, enough protein and strength work, muscle loss shrinks a lot.
Is it possible to lose fat without losing muscle mass?
Yes, and it is the sensible goal: lose fat and keep the muscle you have. It works best when the deficit is moderate, you are not already very lean and you keep up strength training. Gaining muscle at the same time is possible mainly for beginners or people returning after a break.
A calorie deficit that does not eat the muscle
Losing fat means spending more energy than you eat, which is called a calorie deficit. The problem comes when that deficit is stretched too far: the body turns to lean mass as well as fat, and your energy expenditure drops on top.
How do you create a calorie deficit without losing muscle?
With a moderate deficit, about 300-500 kcal below what you burn, as a starting point. Pair it with enough protein and strength training, and avoid sharp cuts. If weight loss stalls, adjust a little at a time instead of cutting hard.
How many kilos is it healthy to lose per week?
Between 0.5 and 1 kg a week, which is about 0.5-1 % of body weight. Losing faster almost always drags muscle along, and what drops at the start of a strict diet is mostly water. If you are losing much more each week, the deficit is too big.
Very low-calorie diets belong in a professional's consulting room. Done on your own, they are the classic way to lose muscle and put the weight back on.
Protein: how much and how to spread it
On a deficit, protein protects muscle mass and also keeps you full. The International Society of Sports Nutrition position stand (Jäger et al., 2017) and the work of Helms et al. (2014) place intake on a deficit above the usual. A rough range is 1.6 to 2.2 g per kilo of body weight a day. Very lean people who lift may need more.
| Weight | Protein per day on a deficit (1.6-2.2 g/kg) | Spread over 4 meals |
|---|---|---|
| 60 kg | 96-132 g | 24-33 g per meal |
| 70 kg | 112-154 g | 28-39 g per meal |
| 80 kg | 128-176 g | 32-44 g per meal |
| 90 kg | 144-198 g | 36-50 g per meal |
How much protein do I need to lose fat without losing muscle?
Between 1.6 and 2.2 g per kilo of body weight a day. For a 70 kg person, 112 to 154 g. It is easier to spread it over three or four meals than to pile it into one. If you have kidney disease, check with your doctor before raising your protein.
What should you eat to lose weight but not muscle mass?
Protein at every meal (eggs, fish, lean meat, pulses, dairy), plenty of vegetables and fruit, good-quality carbohydrate around training and few ultra-processed foods.
There are more ideas in the list of high-protein foods. If you struggle to reach the figure with food, a shake helps. JustLoading chocolate whey gives 22.4 g of protein per 30 g, with 1.4 g of carbohydrate and 121 kcal. If you are wondering about L-carnitine, it does not make you lose weight on its own; the article on what L-carnitine is for explains it.
Strength training: what really protects muscle
What should you do to lose weight without losing muscle mass?
Train strength 2 to 4 days a week and keep the loads you already lift, without lowering them because you are dieting. The muscle then gets the signal that it is needed, which is what makes the deficit take fat rather than lean tissue. Eat protein every day and sleep well.
Cardio adds energy expenditure, but on its own it does not protect muscle. The comparison between the two is in cardio or strength, which first.
Rebound weight gain and how to avoid it
What is rebound weight gain?
It is regaining the weight you lost, and sometimes more, after a very restrictive diet. In those diets a large part of what you lose is water and muscle. When you go back to eating normally, your energy expenditure is lower than before and fat builds up easily.
Five ideas help avoid it:
- Skip miracle diets and the rush: do not try to undo in weeks what was not done in a year.
- Change habits gradually, and see a specialist, because every body is different.
- Be physically active regularly, to keep energy expenditure and muscle.
- Choose filling foods, rich in protein, fibre and water, such as fish, eggs, pulses and fruit.
- Get enough protein, which protects muscle mass.
A quick test: if you doubt a diet, ask yourself whether you could keep it up a year from now.
Habits that add up
Cut back on ultra-processed foods (industrial pastries, ready meals), which carry many calories and little fullness. Watch your carbohydrate portions without removing them, since they fuel training. Drink water, which helps keep hunger in check. And leave out alcohol: it is calories with no nutritional benefit.
Does sleep affect losing fat without losing muscle?
Yes. In a small trial of people on a diet, those who slept 5.5 hours instead of 8.5 lost less fat and more lean mass on the same calories. Sleeping 7 to 9 hours helps the deficit work in favour of muscle.
The trial is by Nedeltcheva et al. (2010), with few participants, so it is a guide and not a promise.
There is no miracle diet and none that suits everyone. A registered dietitian can adjust yours to your weight, your training and your health.
