How to Lose Fat Without Losing Muscle

When most people start a diet, the goal is usually simple: lose fat. But here’s something many don’t realise — you don’t just lose fat, you lose muscle too. And that matters.

Muscle isn’t just about looking toned. It keeps your metabolism healthy, makes daily life easier (think lifting shopping bags, climbing stairs, running after kids), and protects your long-term strength. So when you’re losing weight, protecting muscle should be just as important as losing fat.

Why We Lose Muscle in a Calorie Deficit

To lose fat, you need to be in a calorie deficit — that means eating fewer calories than your body burns. At first, your body uses stored carbs (called glycogen) for energy. Glycogen holds water, so when it’s used up, you’ll notice a quick drop on the scales — that’s the famous “water weight.”

After a few days, your body starts tapping into fat stores. Sounds ideal, right? The issue is, not every part of your body can run on fat — your brain, for example, still needs glucose. If you’re not eating enough, your body may break down protein from your muscles to make that glucose. And that’s where muscle loss creeps in.

How Much Muscle Do You Actually Lose?

The amount varies, but research shows that for every 10% of bodyweight lost, around 20% of that weight comes from lean tissue (like muscle). So yes, even if you diet slowly, some muscle loss is almost inevitable.

Things like genetics, age, and even ethnicity play a role in how much muscle is lost. But the bigger the weight drop, the more muscle you’re likely to lose unless you take steps to protect it.

Carbs Are Not the Enemy

This is where carbs play an important role. Carbohydrates are your body’s main source of fuel — especially for your brain and your muscles when you train. The problem isn’t carbs themselves, it’s when we eat more than our body needs or we’re relying too heavily on processed sources (like white bread, snack bars, and pastries).

In fact, cutting carbs too aggressively can make it harder to train properly, which means your body has even less reason to hold on to muscle. Instead, balance your carbs with your activity level and make sure they don’t crowd protein off your plate.

Protein: How Much Do You Really Need?

Protein is your muscle’s best friend when you’re in a calorie deficit. It helps reduce the amount of muscle your body breaks down, especially if you’re active.

• For general health, 0.8g of protein per kg of bodyweight per day is enough.

• If you’re dieting and exercising, aim for 1.2–1.5g/kg per day.

• If you train hard, you might go a bit higher (up to around 2g/kg).

What about super high protein diets? For healthy people, intakes up to about 2–2.2g/kg/day are considered safe. Going much higher (above ~2.5g/kg) doesn’t seem to provide extra benefits for muscle and might interfere with things like blood sugar control. If you already have kidney or liver issues, then high protein intakes can be risky — so it’s best to stay moderate.

Why Exercise is Non-Negotiable

The most powerful way to tell your body to hold on to muscle is through exercise, especially resistance training.

• Strength training (weights, bands, bodyweight) signals your body to keep and even build muscle.

• Cardio/endurance exercise supports fat loss and overall health, but on its own it’s not as effective for muscle protection.

• The winning combo is both — lift to keep muscle, move more for fat loss.

  
  

Don’t Forget NEAT

While workouts are important, the movement you do outside the gym matters just as much. This is called NEAT (non-exercise activity thermogenesis) — all the calories you burn through things like walking, gardening, housework, playing with your kids, or even just standing instead of sitting.

NEAT can add up to hundreds of calories burned each day and plays a huge role in fat loss without forcing your body into deeper muscle breakdown. Think of it as your secret weapon: it doesn’t feel like “exercise,” but it makes a massive difference.

The Long Game: Sustainability Wins

Even if you do everything right, dieting changes your metabolism and hunger hormones, which is why many people regain weight. Quick fixes make this worse.

The real key is finding a way of eating and moving that you can keep up for life. Slow, steady fat loss, enough protein, resistance training, and daily movement will give you the best chance of keeping fat off while protecting your strength.

Key Takeaways

• Some muscle loss is unavoidable, but you can minimise it.

• Aim for 1.2–1.5g protein per kg of bodyweight daily.

• Balance carbs with your activity — don’t cut them completely.

• Prioritise strength training, but remember NEAT adds up too.

• Avoid extreme diets. Sustainable changes always win.

References

• Cava E. et al. Preserving Healthy Muscle during Weight Loss. Advances in Nutrition, 2017.

• McCarthy J. et al. Weight Loss Strategies and the Risk of Skeletal Muscle Loss. Nutrients, 2021.

• Kokura Y. et al. Higher Protein Intake and Muscle Preservation in Weight Loss: A Meta-Analysis. Clinical Nutrition, 2024.