Body recomposition: how to lose fat and build muscle at the same time

Losing fat and gaining muscle together

That's body recomposition: your shape changes even if your weight barely moves. It comes from progressive strength training, enough protein and, if you have fat to lose, a small calorie cut.

Sources 1, 2

It usually happens when you start lifting

In 114 trials of 4,184 people with overweight or obesity, strength training alone added about 0.8 kg of lean mass and took off about 1 kg of fat compared with not training, across ages and sexes. Older women training 3 times a week for 24 weeks gained 2 to 5% more muscle and lost 2 to 4% of their fat.

Sources 3, 2

Slower if you're lean and trained

It can happen in trained lifters, but the evidence is thinner: a narrative review and one 8-week trial with wide differences between people. Strength athletes grew no muscle in 21 weeks of training, and most lean athletes on a diet lost some lean mass.

Sources 1, 4, 5, 6

Eat at maintenance, or a little less

A deficit of about 500 calories a day stopped muscle gain on average, though strength still rose. Athletes losing 0.7% of their body weight a week gained lean mass, while those aiming for 1.4% didn't.

Sources 7, 8

Protein high, training progressive

Use our protein calculator's building-muscle setting, 1.6 to 2.2 g per kg a day. Strength train at least 3 times a week if you can, adding reps and then weight.

Sources 9, 10, 1

Cardio, sleep, and the right measures

About 150 minutes of cardio a week helps the fat loss and doesn't cost muscle. Sleep 7 to 9 hours. Judge progress by your waist, photos and lifts: bathroom body-fat readings were kilos out.

Sources 11, 12, 13, 14, 15, 16

Two changes at once

Gaining muscle and losing fat over the same period, so your body composition improves even if your weight stays much the same. Researchers use the same definition, and they measure it with body scans.

Sources 1, 2, 17

Why it's possible

Training and protein drive muscle growth, while eating a little less draws on your fat. A small calorie cut doesn't stop muscle gain on average, but a bigger one does. Fat doesn't turn into muscle; the two can change in opposite directions at the same time.

Sources 7, 8, 18

"Skinny fat"

A search term rather than a diagnosis: a healthy or low weight with little muscle and some fat, often around the middle (our description). For most people it's a recomposition case: eat at maintenance, get enough protein and train every muscle progressively.

Source 3

People new to liftingStrong evidence

In 114 trials of 4,184 people with overweight or obesity, strength training alone cut body fat by 1.6 percentage points and fat mass by 1.0 kg, and added 0.8 kg of lean mass, against no training. With a calorie cut as well, fat mass fell by 5.3 kg while lean mass held steady. The results held across ages and sexes.

Source 3

Older adultsEmerging evidence

In 130 untrained older women (average age 69) training 3 times a week for 24 weeks on their usual diets, muscle rose by 2.3% in those eating the least protein and by about 5% in the others, while fat fell by 2 to 4%. It's a pooled analysis of 6 studies.

Source 2

More fat at the start? Not alwaysEmerging evidence

Lean athletes who kept or gained lean mass on a diet mostly had more body fat, a smaller cut or new training. But in 99 older women on the same 24-week programme, those with the least fat at the start recomposed the most. So "more fat, more recomposition" isn't a rule.

Sources 4, 17

Trained lifters: possible, slower, less certainEmerging evidence

A narrative review lists several trials in resistance-trained people that showed recomposition, mostly with high protein; two fitness businesses paid its open-access fee. In one 8-week trial of 48 trained adults, eating 2.3 or 3.4 g of protein per kg both added 1.5 kg of fat-free mass, and the higher-protein group lost 1.7 kg of fat, but some people gained up to 7 kg of fat-free mass while others lost some. Strength athletes didn't grow at all in 21 weeks of training, and most lean athletes on a diet lost some lean mass.

Sources 1, 5, 4, 6

Coming back after a breakMixed evidence

Strength comes back quickly. In 6 women, muscle fibres kept much of their size through 30 to 32 weeks off and regrew fast; in 19 adults, a previously trained leg didn't regrow faster than an untrained one after 20 weeks off. Whether "muscle memory" speeds things up is unsettled.

Sources 19, 20

Eating too little stalls muscle gainStrong evidence

In pooled trials, training while eating less than your needs held back lean-mass gains but not strength gains, and a deficit of about 500 calories a day stopped lean-mass gain.

Source 7

Losing weight slowly kept the gainsEmerging evidence

In 24 elite athletes lifting 4 times a week, those losing about 0.7% of their body weight a week gained 2.1% lean mass and lost 31% of their fat; those aiming for 1.4% a week gained no lean mass.

Source 8

Strength training keeps muscle while you dietStrong evidence

In 119 adults over 8 months, aerobic training took off more fat, strength training added more lean mass, and both together did both. Strength training cut the lean mass lost while dieting by about 0.8 kg in an overview of reviews, and prevented about 93% of it in 6 trials in older adults with obesity.

Sources 21, 22, 23

Strength training trims fat on its ownStrong evidence

Against no exercise, strength training cut body fat by about 1.5 percentage points and fat mass by about half a kilo, including some deep belly fat. The review looked at 58 studies and pooled 54.

Source 24

More protein helps when you eat lessStrong evidence

On calorie-restricted diets, higher protein kept about 0.4 kg more lean mass and took off about 0.9 kg more fat across 24 trials. In 40 young men on a 40% calorie cut training hard 6 days a week, 2.4 g of protein per kg gained 1.2 kg of lean mass and lost 4.8 kg of fat in 4 weeks, against 0.1 kg and 3.5 kg on 1.2 g. That was a proof of principle, not a plan.

Sources 25, 18

Sleep shifts what you loseEmerging evidence

In 10 adults on the same 14-day diet, sleeping 5.5 rather than 8.5 hours cut the fat lost from 1.4 to 0.6 kg and raised the lean mass lost from 1.5 to 2.4 kg.

Source 14

Cardio doesn't cost muscleStrong evidence

Across 43 studies, adding aerobic exercise didn't reduce muscle growth or maximal strength. Each extra 30 minutes a week took off about 0.5 kg and half a centimetre of waist in 116 trials.

Sources 13, 12

At a healthy weight: eat at maintenance

If you mainly want more muscle and less fat, eat at your maintenance calories; the training does the work. Our calories per day calculator gives the figure.

With fat to lose: a small cut

About 300 to 500 calories a day below maintenance, aiming to lose about 0.5% of your body weight a week or less. That's our editorial range, as our recomposition plan uses, smaller on purpose than the NHS's 600 calories a day and 0.5 to 1 kg a week for weight loss. Our calories calculator takes 600 off for weight loss, so take less for recomposition.

Sources 7, 8, 26, 27

Protein: the building-muscle setting

Use our protein calculator's building-muscle setting rather than its weight-loss setting: 1.6 to 2.2 g per kg of body weight a day under 65, spread over 3 to 5 meals. Lean, trained people eating less may keep more muscle with 2.3 to 3.1 g per kg, which is above what the calculator gives and more than most people need.

Sources 9, 10, 4

Strength training is the base

Train every major muscle at least 3 times a week if you can, building towards 10 or more hard sets per muscle a week, stopping 2 or 3 reps short on big lifts and adding reps and then weight. Our full-body gym workouts A and B do this.

Sources 28, 29, 1

Cardio for the fat-loss half

Aim for about 150 minutes a week of moderate activity, counting brisk walks, at a pace where you can talk but not sing. Our recomposition plan holds it there rather than building higher, so you recover for the strength days.

Sources 11, 12, 13

Sleep 7 to 9 hours

That's what adults need, and short sleep shifted what people lost on a diet from fat to muscle.

Sources 15, 14

Your waist, the NHS wayStrong evidence

Find the bottom of your ribs and the top of your hips, wrap a tape midway between them (usually just above your belly button), breathe out naturally and read it, every 4 weeks. NICE counts a waist under half your height as healthy for adults with a BMI under 35.

Sources 30, 31

Photos and your training log

Photos from the front, side and back in the same light and pose, and the weights and reps you lift (our suggestion).

Not bathroom body-fat readingsEmerging evidence

Three smart scales were 2.2 to 4.4 kg of fat out against a body scan, and 15 bioimpedance devices read from 3.5 percentage points too low to 11.7 too high, though some tracked change over 12 to 16 weeks better. NICE says not to use bioimpedance instead of BMI.

Sources 16, 32, 30

Even scans disagreeEmerging evidence

A DEXA scan's error for body fat is about 1.6 percentage points, so some changes reported in recomposition studies are within it, and different measures of muscle growth often disagree. Judge by the trend over months.

Sources 1, 33

Months, not weeks

Trials ran from 4 to 24 weeks. More typical results were just under a kilo of lean mass over a programme in people with overweight or obesity, and a few per cent more muscle over 24 weeks in older women; the fastest change came from 4 extreme weeks of six hard sessions a week and a 40% calorie cut.

Sources 3, 2, 18

Slower than doing one thing at a time

Fat comes off more slowly than with a bigger cut, and muscle grows more slowly than when you eat enough, because a deficit held back muscle gains in pooled trials. That's the trade.

Source 7

No one can promise a look

People differ hugely, so compare yourself with your own week 1. Nobody can promise you a date or a look.

New, coming back, or with fat to lose

Recompose: it's what usually happens anyway when people start strength training.

Source 3

Lean and experienced

A focused muscle-building phase with a small surplus, then a separate slow fat-loss phase, is likely faster; recomposition for you will be slow. Our bulk-up guide covers the first half.

Sources 4, 6

Waist more than half your height

Fat loss comes first for your health, with strength training to keep your muscle.

Sources 30, 27

Women and over 40

Women gain a similar share of muscle to men from the same training, and older women gained muscle and lost fat over 24 weeks. Our plans for women over 40 and 50 add bone and pelvic floor work.

Sources 34, 2

Who shouldn't cut calories

Don't cut calories if you're pregnant: the NHS says pregnancy isn't the time to go on a diet, so use our pregnancy plan, and if you're breastfeeding, the calories calculator's breastfeeding setting with no cut. Don't cut if you're underweight or losing weight without trying, which needs a GP first, or if you're under 18, unless a professional advises it.

If you take insulin, or diabetes tablets such as gliclazide or glimepiride, eating less and exercising more can bring on low blood sugar (feeling hungry, sweaty, shaky or dizzy), so agree the plan with your diabetes team first. Exercising too much, or spending a lot of time worrying about your weight and body shape, are among the NHS's signs of an eating disorder; it says to see a GP as soon as you can.

Losing too fast

Losing weight much faster than planned, with dizziness or exhaustion, means eating more, and seeing a GP if it carries on (our suggestion).

Stop and get medical help

If you get chest pain or pressure, feel faint or dizzy, are unusually breathless, or your heart races or beats irregularly during exercise, as our plans advise.

Call 999 (911 in the US)

For chest pain that comes on suddenly and doesn't go away, feels tight or like squeezing, spreads to your arms, neck, jaw, stomach or back, or comes with sweating, feeling sick, light-headedness or breathlessness; severe difficulty breathing; someone who faints while exercising; palpitations that don't go away, or come with chest pain, shortness of breath or feeling faint; or a headache that starts suddenly and is extremely painful, especially while lifting or straining, or comes with numbness or weakness, difficulty speaking or loss of vision. The NHS says a bleed on the brain may be more likely when lifting something heavy. Don't drive yourself to A&E.

Sources 35, 36, 37, 38

Ask for an urgent GP appointment or call NHS 111

Ask for an urgent GP appointment or get help from NHS 111 for a headache that's triggered or made worse by coughing, sneezing, bending down or exercising. In the US, contact your doctor or urgent care.

Source 39

Back pain that needs 999 or A&E

Call 999 or go to A&E: loss of feeling or numbness around the genitals or bottom, new trouble peeing or controlling your bladder or bowels, changes in genital sensation during sex or problems with erections or orgasm, or pain, tingling, weakness or numbness in both legs. These are signs of cauda equina syndrome, which needs treating in hospital urgently. Don't drive yourself.

Source 40

Hernia

See a GP if you think you have a hernia, a bulge or lump that may get bigger when you strain and smaller when you lie down. Get help from NHS 111 if you have a hernia and pain in or around it, a bloated tummy, you feel or are sick, you're vomiting blood or your vomit looks like coffee grounds, you're constipated, you have a high temperature or feel hot, cold or shivery, or you've suddenly become confused. Call 999 or go to A&E for a femoral hernia (a small lump at the top of your thigh, in your groin) with very bad tummy pain, sickness, being unable to fart or poo, a high temperature or sudden confusion.

Sources 41, 42

Before you start

Speak to your GP first if you haven't exercised for some time or have medical conditions or concerns, as the NHS advises. Get advice before heavy lifting or hard straining work if your blood pressure is uncontrolled, or you have heart disease or chest pain when you're active, a pacemaker or defibrillator, diabetic eye disease, glaucoma, a hernia, recent eye or tummy surgery, or you're pregnant, as our breathing guide lists. After a recent shoulder dislocation or shoulder surgery, follow our shoulder dislocation guide or your surgical team first.

Help to lose weight

The NHS suggests seeing a GP if your BMI is in the overweight or obese range and you want help to lose weight, your waist is more than half your height, or you have conditions such as diabetes, high blood pressure or sleep apnoea.

Source 27

When eating, training or your body becomes a worry

The NHS lists spending a lot of time worrying about your weight and body shape, eating very little food, exercising too much, and having very strict routines around food among the signs of an eating disorder, and says to see a GP as soon as you can. Worrying a lot about one area of your body can be body dysmorphic disorder. Beat's helpline in England is 0808 801 0677, and our eating disorders guide has the other numbers.

Sources 43, 44, 45

"You can't lose fat and build muscle at the same time"Strong evidence

Across 114 trials, strength training added lean mass and took off fat together, older women gained muscle and lost fat over 24 weeks, and young men in a large calorie cut gained 1.2 kg of lean mass while losing 4.8 kg of fat. It's most reliable in beginners and people with fat to lose.

Sources 3, 2, 18

"Recomposition only works for beginners"Mixed evidence

A narrative review lists trials in trained people that showed it, and trained adults gained fat-free mass in 8 weeks on high protein. But strength athletes grew no muscle in 21 weeks, and most lean dieting athletes lost some lean mass. It works for trained lifters, more slowly and less reliably.

Sources 1, 5, 6, 4

"Fat turns into muscle"Strong evidence

They're different tissues. They can change in opposite directions at once, which is what recomposition is.

Source 18

"A bigger calorie cut gets you there faster"Strong evidence

A deficit of about 500 calories a day stopped lean-mass gains, and faster weight loss cost athletes their lean-mass gains.

Sources 7, 8

"If the scales don't move, it isn't working"Strong evidence

Recomposition can leave your weight much the same. Your waist, photos and lifts tell you more, and bathroom body-fat readings were kilos out.

Sources 16, 32, 2

"Cardio kills your gains"Strong evidence

Across 43 studies, cardio didn't reduce muscle growth or maximal strength.

Source 13

"Muscle memory brings everything back in weeks"Mixed evidence

Strength and fibre size came back quickly in one small study of women, but in another, a previously trained leg didn't regrow faster than an untrained one.

Sources 19, 20