Body Recomposition: Can You Lose Fat and Build Muscle at Once?

What body recomposition means, and why the scale hides it

There is no formal definition. A 2020 review from the University of Tampa puts it plainly: "Despite the lack of standardized terminology, building muscle and losing fat concomitantly has been referred to as body recomposition by practitioners." The authors note the common view that it only happens to beginners and to people with a lot of fat to lose, and they set out to challenge it by collecting studies where people who already trained did it too. They name two factors that matter, progressive resistance training and the nutrition that goes with it, and they spend a section on the limits of how body composition gets measured.¹ It is a narrative review, so the authors chose which studies to discuss rather than pooling every trial by a fixed method, and I have gone to the trials themselves below.

The reason recomposition is confusing to track is arithmetic. Lose a kilogram of fat and gain half a kilogram of muscle and the scale says you lost half a kilogram. Gain as much as you lose and it says nothing happened. Calorie tracking sees what went in, the scale sees the total, and neither sees the split. That is the same point the post on whether you need to track macros makes about protein during a diet: almost the same weight loss, made of different tissue.

Four weeks, a 40% deficit, and 1.2 kg of lean mass gained

The trial quoted most often is Thomas Longland's, from Stuart Phillips' lab at McMaster in 2016. Forty young men were randomly assigned, 20 to a group, to four weeks of diets the researchers provided, about 40% below their energy needs. One group ate 1.2 g of protein per kilogram of body weight a day and the other 2.4 g. Both did resistance training and high-intensity interval training six days a week. Body composition was measured with a four-compartment model, which is more careful than a single scan.²

Lean body mass rose by 1.2 kg (give or take 1.0) in the higher-protein group and by 0.1 kg in the other. The higher-protein group also lost more fat, 4.8 kg against 3.5 kg. Every measure of exercise performance improved, and by the same amount in both groups, so the extra protein changed the body composition and not the fitness.²

The authors call it a proof-of-principle trial, and it should be read as one. It ran for four weeks, in young men, with every meal supplied and six training sessions a week. A 40% deficit is far bigger than anyone should run on their own, and I am not suggesting it. The detail I find most useful is the quieter one: even the group on 1.2 g/kg, half the protein, did not lose lean mass while losing 3.5 kg of fat in a month.

Sixteen weeks in women with overweight, and who paid for it

The same lab ran a longer trial in a different population. Ninety premenopausal women with overweight or obesity were put on a diet 500 calories a day below their estimated needs, plus daily aerobic exercise meant to burn 250 more, for 16 weeks. Twice a week they also did resistance training, every session supervised. The three groups differed in protein and dairy: 30% of calories from protein with half of it from dairy, 15% with half from dairy, or 15% with almost none.³

All three groups lost about the same weight. What it was made of differed. Measured by DXA scan, the high-protein group gained 0.7 kg of lean mass over the 16 weeks, the middle group held steady (minus 0.2 kg, not a significant change) and the low-dairy group lost 0.7 kg. In the second half of the trial the high-protein group also lost more fat. The authors report it worked out to about 1.3 g of protein per kilogram a day.³

Before leaning on it, know that protein and dairy went up together, so the trial cannot say which one did the work. Nine women dropped out after week 8. And it was funded by the Dairy Farmers of Canada and the Dairy Research Institute, along with the Canadian Institutes of Health Research.³ None of that makes the numbers wrong, but it is worth knowing who asked the question. The 30% protein share is close to the 28% MyPlate sets on a weight-loss goal, which is one reason I wanted to read this one carefully.

Why a calorie deficit makes muscle harder to build

A deficit slows the process that builds muscle, at least at rest. A study from RMIT University in Melbourne measured how quickly 15 young men and women made new muscle protein after five days of eating 30 calories per kilogram of fat-free mass instead of 45. At rest, the rate was 27% lower than when they had been eating enough. One session of resistance exercise brought it back up to the rate they had at energy balance, and 15 g or 30 g of whey protein after the session pushed it about 16% and 34% above that.⁴ That is a laboratory measurement over hours, not muscle gained over months, but it shows the mechanism: the deficit lowers the baseline and training plus protein lift it again.

Over months, the clearest summary is a 2022 meta-analysis from the Technical University of Munich of randomised trials in which people did resistance training in a calorie deficit for at least three weeks. Compared with people training without a deficit, gains in lean mass were impaired (effect size minus 0.57) but gains in strength were not significantly different (minus 0.31, p=0.28). Across all the trials, a deficit of around 500 calories a day was where lean mass gains stopped. The authors advise people training to preserve lean mass during weight loss to avoid deficits larger than 500 calories a day.⁵

That figure is a line fitted through many trials, and single trials land on either side of it. Longland's men ran a much larger deficit and still gained lean mass, with very high protein and six supervised sessions a week. For anyone without that setup, 500 calories a day is the more useful number.

Who recomposes, and who mostly does not

For people who have never trained, a deficit may not be needed at all. A Brazilian analysis pooled 130 untrained women with an average age of 69 from six resistance training studies, 24 weeks each, three sessions a week. Skeletal muscle mass went up in every group and fat mass went down. Split by how much protein the women already ate, muscle rose 2.3% in the lowest third against 5.4% and 5.1% in the two higher thirds, and fat fell by 1.7%, 3.7% and 3.1%, differences that were not significant.⁶ This was a retrospective analysis grouped by habitual intake, not a trial that assigned protein, so the protein figure may be standing in for something else about those women. The recomposition itself happened in all of them. The post on counting calories after 60 covers what dieting without training costs at that age.

A smaller McMaster trial makes the point about the deficit more directly. Twenty young women who had not been dieting did whole-body resistance training five days a week for 12 weeks and drank either fat-free milk or a carbohydrate drink with the same calories after each session. The milk group gained 1.9 kg of lean mass and lost 1.6 kg of fat, while their weight went up by 0.5 kg, a change that was not significant. The carbohydrate group gained 1.1 kg of lean mass and 0.86 kg of weight, and their fat mass did not change significantly.⁷ Ten women a group is very small, and like the 16-week trial it was testing milk. But nobody in it was trying to lose weight, and the milk group still recomposed.

At the other end, a Norwegian trial took 24 elite athletes doing four resistance sessions a week and assigned them to lose 0.7% or 1.4% of their body weight a week. Both groups lost about 5.5% of their weight, the slow group over 8.5 weeks and the fast group over 5.3. Lean body mass rose 2.1% in the slow group and did not change in the fast one (minus 0.2%).⁸ Twenty-four people is small, but these were trained athletes, and the slower pace is what let them gain.

What I could not find is a single trial that put beginners and experienced lifters through the same protocol and compared how much each gained. The Tampa review argues trained people can recompose too, and the athletes above did.¹⁸ How much smaller the effect gets as you get leaner and more trained is a question I cannot answer from the trials, so I will not put a number on it.

You probably cannot measure it at home

The changes in these trials are around a kilogram of lean mass over one to four months. Most people trying to check for that own a bathroom scale that estimates body fat by passing a small current through the feet, called bioelectrical impedance (BIA). Researchers at Texas Tech tested 15 BIA devices, 14 of them consumer models, against a laboratory four-compartment model in 73 adults. The devices were very repeatable, with precision errors of 0 to 0.49%. They were much less accurate: average error ranged from 3.5 percentage points of body fat too low to 11.7 too high, depending on the device.⁹

For recomposition, the more relevant part is change. Thirty-seven people came back 12 to 16 weeks later, and the devices' estimates of how their body fat had changed carried standard errors of 1.7 to 2.6 percentage points. The authors concluded that select models, particularly the octapolar ones with hand and foot electrodes and some foot-to-foot scales, may be useful for tracking change when a research device is out of reach.⁹ For a 75 kg person, 2 percentage points of body fat is 1.5 kg, more than the lean mass the women in the 16-week trial gained.

A laboratory DXA scan is better but has its own blind spot. "Lean mass" on a DXA is everything that is not fat or bone, and that includes water and stored carbohydrate. In a study at the University of Limerick, 12 active men exercised in the heat until they lost 1.93 kg, and DXA lean mass fell by 1.69 kg. Two days of high-carbohydrate eating then raised body mass by 2.53 kg and DXA lean mass by 2.36 kg. Fat mass did not change at any point.¹⁰ At the Australian Institute of Sport, carbohydrate loading in 18 trained cyclists raised DXA lean body mass by 2 to 3%, in a period when, in the authors' words, "minimal change in muscle protein mass is likely".¹¹

So a weekend of pasta can move a DXA reading by about as much as months of recomposition, and a low-carbohydrate start to a diet can look like muscle loss that is mostly water and glycogen. The trials controlled for this with standard conditions before each scan, which is the part people skip when they buy a single scan before and after.

A tape measure does not solve it either. In the 16-week trial, the waist shrank by about 5 cm in every group, the women who gained lean mass and the women who lost it alike.³ It shows fat coming off. It cannot show what happened to the muscle. Strength is not proof either: the Munich meta-analysis found strength kept improving in a deficit even when lean mass gains stalled.⁵

What the evidence does not settle

• How long it lasts. The trials here ran from 4 to 24 weeks. None of them followed people for a year to see whether the extra lean mass stayed.²³⁶
• How much protein is enough. Longland's lower group held its lean mass on 1.2 g/kg, the women who gained did it on about 1.3, and the higher figure that gained most was 2.4 under conditions nobody lives in.²³ Why the recommended protein targets disagree is the subject of why macro calculator apps disagree about your protein target.
• Whether the lean mass is muscle. DXA and BIA count water and glycogen as lean, and the gains in these trials are about the size of the error.⁹¹⁰¹¹
• How much training age matters. No trial I found compared beginners and experienced lifters directly.¹
• Who funded the question. The 16-week trial with the protein share closest to MyPlate's was paid for partly by the dairy industry and could not separate protein from dairy.³

What a macro tracking app can see here, and what it cannot

A macro tracking app sees what you tell it you ate. MyPlate estimates calories and macros from a photo or a sentence, so the protein figure for a meal is an estimate, not a measurement, and there is no food database or barcode scanner behind it. It does not know whether you lift. The only place exercise enters the plan is the activity level you pick at setup, and the app does not add workouts back on top; the exercise calories post explains why I built it that way. It cannot see body composition at all, and logging a new weight does not recompute your targets.

Tracking macros for fat loss while you build muscle

Here is what the arithmetic looks like in practice, using the numbers MyPlate would give. A 30-year-old man, 180 cm and 85 kg, moderately active, gets an estimated maintenance of 2,836 calories and a weight-loss target of 2,411, which is 15% below, or 425 calories a day. Protein at 28% of that is 168 g, about 2.0 g per kilogram. A 35-year-old woman, 165 cm and 68 kg, moderately active, gets 2,132 at maintenance and 1,811 to lose, a 320-calorie deficit, with 126 g of protein, about 1.85 g/kg.

Both deficits sit under the 500-calorie line from the Munich meta-analysis, and both protein figures sit above what the two McMaster trials used for their lower groups.²³⁵ But the deficit is a percentage, so it grows with the person. Put the same man on the highest activity setting and 15% is 522 calories, just over the line. Smaller and less active people get smaller deficits, which suits recomposition and makes the fat loss slower.

• Lift, and add weight or repetitions over time. Every recomposition above came with resistance training: twice a week for the women in the 16-week trial, three times for the older women, four for the athletes.³⁶⁸
• Keep the deficit modest. Under about 500 calories a day, or a pace closer to the athletes' 0.7% of body weight a week than 1.4%.⁵⁸ How pace affects regain, apart from muscle, is in fast or slow weight loss.
• Check the protein in grams against your weight. In MyPlate protein is a share of calories, so if the calorie target falls, so do the grams. Tracking macros for fat loss mostly comes down to this one figure.
• Judge it over months, under the same conditions. Weigh at the same time of day, use the same scale if you use BIA at all, and read the trend rather than one reading. Expect the scale to move slowly, and do not read a stalled scale as failure if your waist and your lifts are moving.⁹
• Do not go under the floor. NIH/NHLBI guidance is not to go below 1,200 calories a day for women or 1,500 for men without medical supervision, and MyPlate's targets stop there.¹²

If chasing a body fat number is making you anxious, or a reading on a scale is deciding how you feel about yourself, stop and talk to a doctor or a registered dietitian. What the research says about who that is most likely to be is in can calorie tracking cause an eating disorder.

Common questions

Lift, eat the protein, judge it in months

Recomposition is real and it is small. The trials found a kilogram or so of lean mass over one to four months, in people who lifted, ate more protein than the minimum and kept the deficit modest or very closely supervised.

Measuring it is where most people go wrong. A bathroom scale cannot see it, a body fat scale guesses with an error bigger than the change, and even a DXA scan moves with what you ate the day before. Log the calories and the protein, keep lifting, and give it longer than feels reasonable before you decide it is not working.

Sources

Every figure above traces to one of these. If you find a number that doesn't match the source it claims, tell me and I'll correct it.

1. Barakat C, Pearson J, Escalante G, Campbell B, De Souza EO (2020). Body recomposition: can trained individuals build muscle and lose fat at the same time? Strength and Conditioning Journal, 42(5):7-21. Read the review →
2. Longland TM, Oikawa SY, Mitchell CJ, Devries MC, Phillips SM (2016). 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, 103(3):738-746. Read on PubMed →
3. Josse AR, Atkinson SA, Tarnopolsky MA, Phillips SM (2011). Increased consumption of dairy foods and protein during diet- and exercise-induced weight loss promotes fat mass loss and lean mass gain in overweight and obese premenopausal women. Journal of Nutrition, 141(9):1626-1634. Read on PubMed →
4. Areta JL, Burke LM, Camera DM, et al. (2014). Reduced resting skeletal muscle protein synthesis is rescued by resistance exercise and protein ingestion following short-term energy deficit. American Journal of Physiology: Endocrinology and Metabolism, 306(8):E989-E997. Read on PubMed →
5. Murphy C, Koehler K (2022). Energy deficiency impairs resistance training gains in lean mass but not strength: a meta-analysis and meta-regression. Scandinavian Journal of Medicine and Science in Sports, 32(1):125-137. Read on PubMed →
6. Ribeiro AS, Pereira LC, Schoenfeld BJ, et al. (2022). Moderate and higher protein intakes promote superior body recomposition in older women performing resistance training. Medicine and Science in Sports and Exercise, 54(5):807-813. Read on PubMed →
7. Josse AR, Tang JE, Tarnopolsky MA, Phillips SM (2010). Body composition and strength changes in women with milk and resistance exercise. Medicine and Science in Sports and Exercise, 42(6):1122-1130. Read on PubMed →
8. Garthe I, Raastad T, Refsnes PE, Koivisto A, Sundgot-Borgen J (2011). 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, 21(2):97-104. Read on PubMed →
9. Siedler MR, Rodriguez C, Stratton MT, et al. (2023). Assessing the reliability and cross-sectional and longitudinal validity of fifteen bioelectrical impedance analysis devices. British Journal of Nutrition, 130(5):827-840. Read on PubMed →
10. Toomey CM, McCormack WG, Jakeman P (2017). The effect of hydration status on the measurement of lean tissue mass by dual-energy X-ray absorptiometry. European Journal of Applied Physiology, 117(3):567-574. Read on PubMed →
11. Bone JL, Ross ML, Tomcik KA, et al. (2017). Manipulation of muscle creatine and glycogen changes dual X-ray absorptiometry estimates of body composition. Medicine and Science in Sports and Exercise, 49(5):1029-1035. Read on PubMed →
12. National Heart, Lung, and Blood Institute, NIH (1998). Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. NIH Publication 98-4083. Read the guidelines →

The formulas and limits behind MyPlate's own numbers, with their citations, are on the health sources page.