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How do you lose fat without losing muscle?

How to Lose Fat Without Losing Muscle

Reviewed · 9 sources · By Anthony Falcone

The short answer: Keep lifting weights, eat more protein than usual, and lose weight slowly, about 0.5–1% of your body weight a week. In trials, resistance training during a diet prevented most of the lean-mass loss, and a higher protein intake protected it further. Don't cut your sleep: in a small study, short nights during a diet shifted the loss from fat towards lean mass.8,1,5,7

Before you start

  • If you have kidney disease, diabetes or take medicine for blood sugar or blood pressure, talk to your doctor before you cut calories or raise your protein intake a lot.
  • If you have, or have had, an eating disorder, talk to your doctor before dieting to get lean. Preoccupation with weight and shape, and binge eating, are common among people who diet hard for their physique, such as competitive bodybuilders.8
  • This guide is for healthy adults. Children, teenagers and pregnancy are outside it; ask your doctor.
  • 93.5% less lean-mass loss when dieters also lifted weights (6 trials, older adults)1
  • 2.3–3.1 g protein per kg a day suggested for lifters in a calorie deficit4
  • 0.5–1% of body weight a week: the pace advised to keep muscle8
  • 500 kcal a day: deficits of about this size stopped lean-mass gains from training2
  • 1.2 kg lean mass gained in 4 weeks on high protein, despite a 40% calorie cut5

Why dieting costs muscle

When you eat less than you burn, you lose some lean mass along with the fat. The bigger the deficit, the larger the share of the weight that tends to come from lean mass, and the leaner you get, the higher the risk.8

That doesn't make weight loss a bad idea. A review of weight loss in people with obesity found that dieting lowers muscle mass without making muscles weaker, and that overall physical function improves, most likely because there is less fat to carry.9

A note on the numbers below: most studies measure lean or fat-free mass: roughly, your weight minus your fat. Lean tissue is mostly water, so lean mass is a stand-in for muscle, not a direct measure of it.7

Lift weights through the whole diet

A meta-analysis of 6 randomised trials in older adults with obesity compared dieting alone with dieting plus resistance training three times a week for 12 to 24 weeks. The lifters lost 93.5% less lean mass (0.819 kg more kept), while fat loss was about the same in both groups.1

The training in those trials was ordinary: a warm-up, then two or three sets of 8 to 15 repetitions for the main muscle groups, at 65% or more of the heaviest weight the person could lift once.1

Endurance exercise also helps keep muscle during weight loss, but in the review of people with obesity, resistance exercise also made them stronger. So cardio is fine; it just doesn't replace lifting.9

Strength holds up better than size. A meta-analysis of trials lasting at least 3 weeks found that a calorie deficit reduced the lean mass people gained from resistance training, but their strength gains were similar with or without the deficit.2

Eat more protein than usual

For exercising people in general, the International Society of Sports Nutrition (ISSN) suggests 1.4–2.0 g of protein per kg of body weight a day. During a calorie deficit it suggests more, 2.3–3.1 g per kg, for resistance-trained people who want to keep as much lean mass as possible. At 70 kg that is 2.3 × 70 = 161 g to 3.1 × 70 = 217 g a day.4

A review on contest preparation for natural bodybuilders gives the same 2.3–3.1 g range, but per kg of lean body mass rather than total weight, which comes to fewer grams. It suggests aiming higher in the range the leaner you are and the bigger your deficit.8

The clearest test: in a 4-week trial, two groups of 20 young men ate about 40% fewer calories than they needed and trained six days a week, combining resistance training with high-intensity intervals. On 2.4 g of protein per kg they gained 1.2 kg of lean mass and lost 4.8 kg of fat; on 1.2 g per kg they gained 0.1 kg of lean mass and lost 3.5 kg of fat.5

The pattern holds in older adults too. A meta-analysis of 20 randomised trials in adults over 50 found that those on higher-protein diets during weight loss (at least 25% of energy from protein, or at least 1.0 g per kg a day) kept more lean mass and lost more fat.3

More is not automatically better. The review of weight loss in obesity notes that high protein helps keep lean mass but didn't improve strength and could have adverse effects on metabolic function, and it recommends adequate but not excessive protein.9

Lose it slowly

The bodybuilding review advises a calorie intake that takes off about 0.5–1% of your body weight a week, and suggests that diets longer than two to four months at that pace keep lean mass better than shorter, more aggressive ones.8

In a trial in 24 elite athletes who did four resistance sessions a week, one group aimed to lose 0.7% of body weight a week (eating 19% less) and the other 1.4% (eating 30% less). Both lost a similar share of body weight, 5.6% and 5.5%, but the slower group lost 31% of its fat mass against 21%, and its lean mass rose by 2.1% while the faster group's didn't change. The slow group took 8.5 weeks on average, the fast group 5.3.6

The deficit-and-training meta-analysis puts a number on it: a deficit of about 500 kcal a day was enough to stop lean-mass gains, and the authors advise people trying to keep lean mass during weight loss to stay under 500 kcal a day.2

Slow down as you get leaner. With less fat available, the risk of losing muscle rises, so the review suggests a more gradual pace towards the end of a diet than at the start.8

Can you lose fat and gain muscle at the same time?

Sometimes, yes. In the 4-week trial above, the high-protein group gained 1.2 kg of lean mass during a 40% calorie cut, and in the athletes' trial the slow-loss group gained 2.1% lean mass while losing fat.5,6

Both were short trials in young people training hard. Across trials, a deficit reduces the lean mass people gain from training. So the realistic goal for most people is to keep their muscle while they lose fat, and to count any gain as a bonus.2,5,6

Protect your sleep

In a crossover study, 10 overweight adults ate the same reduced-calorie diet for 14 days twice: once with 8.5 hours in bed a night and once with 5.5. Weight loss was similar, about 3 kg, but with short nights they lost 0.6 kg of fat instead of 1.4 kg, and 2.4 kg of fat-free mass instead of 1.5 kg. They were also hungrier.7

It was a tiny two-week laboratory study, and the authors note that its design limited its length and size. Still, it is a reason not to cut sleep to fit in more training while you diet.7

Carbs, fat and meal timing

In studies of lifters on calorie-restricted, high-protein diets, cutting fat while keeping enough carbohydrate appeared to protect lean mass better than lower-carbohydrate, higher-fat approaches. Ketogenic diets have barely been studied in lifters who are dieting, and people respond differently, so the review leaves room for those who do better on more fat and fewer carbs.8

Timing matters much less than totals. Changing when and how often you eat appears to have little effect on fat loss or keeping lean mass. If you want to cover the theory anyway, the review suggests three to six meals a day, with 0.4–0.5 g of protein per kg of body weight in the meals before and after training.8

What to do with this

  • Do resistance training for all the main muscle groups, about three times a week, for the whole diet.1
  • Eat more protein: 1.4–2.0 g per kg a day, or 2.3–3.1 g per kg if you lift and are in a deficit.4,5
  • Aim to lose about 0.5–1% of your body weight a week, keep the daily deficit at about 500 kcal or less, and slow down as you get leaner.8,2,6
  • Keep your sleep. Don't trade it for extra training while you diet.7
  • Judge your training by strength as well as the scale: strength usually holds up in a deficit even when lean mass doesn't grow.2

How sure is this?

  • Most trials here are small and short: the high-protein trial had 40 young men for 4 weeks, the weight-loss-rate trial 24 athletes, and the sleep study 10 adults for two weeks.5,6,7
  • The two meta-analyses on lifting and protein during weight loss studied older adults (with obesity, or over 50). Young, lean lifters were studied in fewer and smaller trials.1,3,8
  • Many authors of the ISSN protein position stand declare ties to supplement companies, and the ISSN is partly funded by companies that sell protein supplements. The bodybuilding review, the resistance-training meta-analysis and the obesity review declare no conflicts of interest.4,8,1,9
  • For five sources (Longland 2016, Garthe 2011, Murphy 2022, Kim 2016, Cava 2017) we could read only the abstract, so we use only the main results reported there.5,6,2,3,9

Common questions

How do I lose fat without losing muscle?

Keep lifting weights, eat more protein than usual, and lose weight slowly, about 0.5–1% of your body weight a week. In trials, dieting with resistance training kept most of the lean mass that dieting alone lost.1,8,4

Can you lose fat and gain muscle at the same time?

Sometimes. Young men on 2.4 g of protein per kg gained 1.2 kg of lean mass during a 4-week, 40% calorie cut while training hard. On average, though, a deficit reduces muscle gain, so keeping your muscle is the realistic goal.5,2

How much protein do I need to keep muscle while losing weight?

The ISSN suggests 1.4–2.0 g per kg of body weight a day for exercising people, and 2.3–3.1 g per kg for resistance-trained people in a calorie deficit.4

How fast can I lose weight without losing muscle?

About 0.5–1% of your body weight a week. In elite athletes, losing 0.7% a week let lean mass rise by 2.1%, while losing 1.4% a week didn't.8,6

Is cardio bad for muscle when cutting?

No. In people with obesity, both endurance and resistance exercise helped keep muscle during weight loss, and resistance exercise also made them stronger, so keep lifting as the base.9

Sources

  1. Sardeli AV, Komatsu TR, Mori MA, Gáspari AF, Chacon-Mikahil MPT. Resistance Training Prevents Muscle Loss Induced by Caloric Restriction in Obese Elderly Individuals: A Systematic Review and Meta-Analysis. Nutrients, 2018. Meta-analysis. doi.org/10.3390/nu10040423
  2. Murphy C, Koehler K. Energy deficiency impairs resistance training gains in lean mass but not strength: A meta-analysis and meta-regression. Scandinavian Journal of Medicine & Science in Sports, 2022. Meta-analysis. doi.org/10.1111/sms.14075
  3. Kim JE, O'Connor LE, Sands LP, Slebodnik MB, Campbell WW. Effects of dietary protein intake on body composition changes after weight loss in older adults: a systematic review and meta-analysis. Nutrition Reviews, 2016. Meta-analysis. doi.org/10.1093/nutrit/nuv065
  4. Jäger R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition Position Stand: protein and exercise. Journal of the International Society of Sports Nutrition, 2017. Position stand. doi.org/10.1186/s12970-017-0177-8
  5. Longland TM, Oikawa SY, Mitchell CJ, Devries MC, Phillips SM. Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial. American Journal of Clinical Nutrition, 2016. Randomised trial. doi.org/10.3945/ajcn.115.119339
  6. Garthe I, Raastad T, Refsnes PE, Koivisto A, Sundgot-Borgen J. Effect of two different weight-loss rates on body composition and strength and power-related performance in elite athletes. International Journal of Sport Nutrition and Exercise Metabolism, 2011. Randomised trial. doi.org/10.1123/ijsnem.21.2.97
  7. Nedeltcheva AV, Kilkus JM, Imperial J, Schoeller DA, Penev PD. Insufficient sleep undermines dietary efforts to reduce adiposity. Annals of Internal Medicine, 2010. Randomised trial. doi.org/10.7326/0003-4819-153-7-201010050-00006
  8. Helms ER, Aragon AA, Fitschen PJ. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition, 2014. Review. doi.org/10.1186/1550-2783-11-20
  9. Cava E, Yeat NC, Mittendorfer B. Preserving Healthy Muscle during Weight Loss. Advances in Nutrition, 2017. Review. doi.org/10.3945/an.116.014506

The Fat Loss Protocol turns this into a plan: your calorie, protein and weekly-loss targets, a plate that keeps you full, eating patterns compared honestly, and your first 4 weeks, plateaus and keeping it off, with 25 peer-reviewed references. For the lifting side, the Hypertrophy Protocol has 3 training split options (3, 4 or 5 days) and a mechanical tension guide. Fat Loss Protocol · Hypertrophy Protocol

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