What is body recomposition?
Body recomposition (“recomp”) means losing fat and building muscle at the same time. Instead of separate bulking and cutting phases, you lift consistently, eat plenty of protein and stay close to maintenance calories, so your weight changes slowly while your shape changes.
How this calculator works
BMR (Mifflin–St Jeor) = 10 × kg + 6.25 × cm − 5 × age + 5 (men) or − 161 (women)
Maintenance = BMR × activity factor
Training days ≈ maintenance · Rest days ≈ 85% of maintenance
Protein = 1.6–2.2 g per kg of body weight
Eating at maintenance on training days fuels your sessions; a modest deficit on rest days drives fat loss. The protein range reflects a 2018 meta-analysis (Morton et al.) in which muscle gains plateaued around 1.6 g/kg, with 2.2 g/kg as a sensible upper end.
Recomp macros
- Protein: the calculator's range, spread over 3–5 meals.
- Fat: at least the amount shown (about 25% of maintenance calories).
- Carbohydrates: the rest of your calories, especially around workouts.
Who recomps best
Beginners, people returning after a break and those with more body fat see the fastest results. Lean, experienced lifters can still recomp, but progress is slower and a dedicated gain or cut may be more efficient.
How to track progress
The scale may barely move. Track waist measurement, progress photos and strength on your main lifts every 2–4 weeks; if strength rises and your waist shrinks, the recomp is working.
How accurate these numbers are
Mifflin–St Jeor predicts resting energy expenditure for most healthy adults to within about 10%, but it was built on population averages: it does not know your body composition, medication, thyroid function or how much you fidget. Activity factors are coarser still. Treat the maintenance figure as a starting estimate, then adjust by what the scale and your waist actually do over 2–4 weeks.
When to get advice before cutting calories
A rest-day deficit is modest by design, and this calculator will not push you into a crash diet. Even so, talk to a doctor or dietitian before eating below your estimated needs if you:
- are under 18, pregnant or breastfeeding;
- have or have had an eating disorder, or find calorie counting distressing;
- have diabetes, kidney disease, or take medication that depends on regular meals;
- are recovering from illness, surgery or injury, or are already underweight.
The protein range here (1.6–2.2 g/kg) is for healthy kidneys. If you have been told to limit protein, follow that advice instead of this page.
Estimates for general fitness use, not a prescribed diet. See the medical disclaimer.
Frequently asked questions
Does body recomposition really work?
Yes, especially for beginners, people returning after a break and those with more body fat. Lifting regularly while eating enough protein lets you lose fat and gain muscle at the same time. Experienced, lean lifters recomp much more slowly.
How much protein do I need to recomp?
Research pooled by Morton et al. (2018) found muscle gains plateau around 1.6 g of protein per kg of body weight per day, with an upper range near 2.2 g/kg. This calculator shows that range.
How long does a recomp take?
Expect visible changes in 8–12 weeks and meaningful ones over 6–12 months. The scale may barely move, so track waist measurements, photos and strength instead.
Sources
The formula on this page comes from the published work below. We check the numbers against the worked examples in these sources with automated tests, and re-read the page against them when we review it.
- Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–247. pubmed.ncbi.nlm.nih.gov/2305711/
- Barakat C, Pearson J, Escalante G, Campbell B, De Souza EO. Body recomposition: can trained individuals build muscle and lose fat at the same time? Strength Cond J. 2020;42(5):7–21. doi.org/10.1519/SSC.0000000000000584
- Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018;52(6):376–384. pubmed.ncbi.nlm.nih.gov/28698222/
General fitness information, not medical advice. Results are estimates; check with a doctor or qualified coach before major changes to diet or training. Formula and copy last reviewed 12 October 2026.