Most people want the same thing from a fat loss phase: to look and feel better, not just lighter. That means holding on to the muscle underneath while the fat comes off. The good news is that it's entirely achievable. The bad news is that most popular approaches — crash diets, very low calories, ditching weights for cardio — actively work against it.
This guide covers the levers that actually matter. Pull them correctly and you'll lose fat at a reasonable pace while keeping most, if not all, of the muscle you've worked for.
1. Keep protein high throughout
Protein is the single most important nutritional variable when you're trying to hold on to muscle in a deficit. It provides the amino acids your body needs to maintain muscle tissue, and it's significantly more satiating than carbohydrates or fats — which makes it easier to stick to a calorie target without feeling constantly hungry.
In a calorie deficit, aim for roughly 1.8–2.2g of protein per kilogram of bodyweight per day. This is somewhat higher than the recommendation for someone building muscle in a surplus, because when calories are reduced, the body is under more pressure to use protein for energy — so you need more of it to ensure enough goes towards maintaining muscle. For a 75kg person, that's in the region of 135–165g daily.
Spread it across your meals. Prioritise whole food sources — chicken, fish, eggs, beef, dairy, tofu, pulses — and use a shake to top up if you're struggling to hit your target on a busy day. Don't overthink the precise number, but do take it seriously. Protein is not optional during a cut.
2. Don't drop the weights — keep lifting heavy
This is where a lot of people go wrong. When the goal switches to fat loss, the instinct is often to drop the weights, go lighter, do more reps and add in more cardio. This approach misunderstands what keeps muscle on your frame.
Your body is pragmatic. It doesn't maintain tissue it doesn't need. Muscle is metabolically expensive — it costs energy just to keep it around. In a calorie deficit, your body is looking for places to cut costs. The only clear signal that tells it your muscle is worth keeping is that you're using it hard.
Heavy resistance training is that signal. If you keep lifting close to your usual loads — challenging weights, taken close to failure, across the same kind of movements — your body has a strong reason to hold on to muscle. If you switch to nothing but circuit classes and light cardio, you remove that signal entirely.
You don't need to set personal bests during a cut, and your performance may dip slightly when calories are lower. That's normal. But keep the intensity up. Maintain your compound lifts. Don't let the weights drop dramatically just because the goal has changed.
What about cardio?
Cardio isn't the enemy of muscle, but it can become a problem if it tips you into an excessively large deficit or if it starts replacing your resistance training rather than supplementing it. Used sensibly — a few sessions a week of moderate-intensity work or simply increasing your daily step count — it's a useful tool for burning a few extra calories without much muscular cost. Just don't let it become the entire strategy.
3. Don't crash the deficit
The more aggressively you cut calories, the harder it is to hold on to muscle. Very low calorie diets — crash diets — create conditions where muscle loss becomes much more likely. Energy availability is so low that your body is forced to break down muscle tissue for fuel, regardless of how much protein you eat or how hard you train.
A moderate deficit is the sensible approach. Targeting a loss of roughly 0.5–1% of your bodyweight per week is a practical guideline that balances progress with muscle retention. For most people that means a deficit of somewhere between 300 and 500 calories per day — meaningful enough to create consistent fat loss, but not so severe that your training suffers and your body starts cannibalising muscle.
Bigger isn't better here. Halving your calories to lose fat faster almost always backfires — you lose muscle alongside the fat, your training performance tanks, and you often end up in a worse position than if you'd taken the slower route.
- Eat 1.8–2.2g protein per kg bodyweight every day.
- Keep lifting heavy — maintain the signal to hold muscle.
- Aim for a moderate deficit: roughly 0.5–1% of bodyweight lost per week.
- Prioritise sleep — poor sleep accelerates muscle loss in a deficit.
- Be patient. Slower fat loss preserves more muscle.
4. Take sleep seriously
Sleep is underrated in almost every fitness context, but it matters especially when you're cutting. During sleep, your body releases growth hormone, repairs tissue and regulates the hormones — including cortisol and testosterone — that influence how much muscle you hold on to.
When sleep is poor or short, cortisol (a stress hormone) tends to rise. Elevated cortisol in a calorie deficit is a particularly unfavourable environment for muscle: it promotes muscle breakdown and can make fat loss harder at the same time. Aim for 7–9 hours, and treat sleep as part of your programme — not an afterthought.
5. Be patient — the rate of loss matters
Perhaps the most underappreciated point in fat loss is simply the pace at which you try to do it. The faster you try to lose fat, the more you compromise muscle. The slower and steadier the deficit, the more of your physique you keep intact.
This requires a degree of patience that most popular diet culture doesn't encourage. Programmes promising dramatic results in short windows nearly always achieve them partly by stripping muscle — you're lighter, but not necessarily leaner in the way you hoped. A 16-week cut at a moderate deficit, done consistently, will almost always leave you in better shape than an 8-week crash that loses weight twice as fast.
Fat loss is not a sprint. Treating it like one tends to cost you muscle, leave you feeling flat, and make it harder to sustain the diet long enough to reach your goal. If you'd like a plan built around your specific situation — one that takes all of this into account from day one — that's exactly what online weight loss coaching is designed to do.