Body recomposition
Body Recomposition Calculator
Estimate maintenance, a calorie and protein target, and a 12-week fat and lean-mass projection. Results depend on the model assumptions and your response.
Updated
What the calculator computes
This calculator estimates maintenance or a 5 to 15 percent deficit, depending on body fat and training experience. It sets protein and projects fat and lean mass separately. These are starting estimates, not guaranteed outcomes. The calculator does not model the full range of calorie intakes at which recomposition may occur.
The model estimates fat and lean mass separately. Lean mass includes muscle, water and other fat-free tissue, so projected lean gain is not measured muscle gain. Scale weight alone cannot separate these changes.
Who body recomposition works best for
Starting body fat and training experience inform this model score. Training, diet and individual response also matter.
How the numbers are derived
Everything starts at maintenance, your Total Daily Energy Expenditure. It is the calorie level where weight holds steady, built from basal metabolic rate times an activity factor. Body fat does not move this number; it shapes the protein target and how deep the deficit is allowed to go.
This tool uses maintenance or a 5 to 15 percent deficit. A deficit is not required for every recomposition.
Protein is set next, at about 2.2 g per kg of lean body mass, and it is treated as a floor rather than a target to hit on average. Fat is held above a hormonal minimum of roughly 0.7 g per kg of bodyweight, and carbohydrate fills whatever calories remain. That is why the macro split reads protein-first: the muscle-protecting input is locked in before anything else moves.
Recomposition model parameters
The exact numbers the calculator runs on, so you can quote or check them. Every value is the one the tool computes with.
| Parameter | Value | What it sets |
|---|---|---|
| Calorie target | TDEE − 0–15% | This tool uses maintenance or a 5 to 15 percent deficit. A deficit is not required for every recomposition. |
| Protein floor | 2.2 g/kg | Per kilogram of lean body mass. The muscle-protecting input, held as a floor rather than an average. |
| Fat floor | 0.7 g/kg | Per kilogram of bodyweight. A hormonal minimum; carbohydrate fills whatever calories remain. |
| Carb floor | 50 g | Minimum grams kept for training and brain fuel before the deficit takes any more. |
| Fat tissue energy | 9,441 kcal/kg | Energy stored per kilogram of body fat (Hall 2008). The denominator of the fat-loss projection. |
| Lean tissue energy | 1,816 kcal/kg | Energy stored per kilogram of lean mass (Hall 2008). Muscle is cheap to build; fat is dense to lose. |
| Lean-gain ceiling, beginner | 1.25% / mo | Natural monthly lean gain as a share of bodyweight in the first training year. |
| Lean-gain ceiling, intermediate | 0.75% / mo | The rate a few years in, once beginner gains are spent. |
| Lean-gain ceiling, advanced | 0.4% / mo | Near the genetic ceiling, where recomposition slows to a crawl. |
| Essential body-fat floor | 5% / 13% | Men / women. Projections clamp here; below it is unsafe, not leaner. |
Tissue energy densities and the natural rate-of-gain bands follow Hall (2008) and the recomposition literature listed under References below.
How calorie balance affects the trade-off
Studies report fat loss with lean-mass gain during some deficits and around estimated maintenance. Lean-mass measurements do not isolate muscle. A slight surplus may also allow recomposition, but this is an inference: reported intake is not a measured energy surplus. Starting body fat, training, protein and individual response all matter.
A deficit can prioritize fat loss, while larger deficits may limit lean-mass gain. Maintenance may better support training for some people. This calculator models maintenance or a 5 to 15 percent deficit; it does not establish where recomposition starts or stops.
Why the scale may miss changes
The chart models fat and lean mass separately. Their combined change gives the projected weight change. These are estimates, not measurements of your tissues. Compare your actual weight trend with waist measurements and training progress over several weeks.
Body-fat estimates taken the same way, waist measurements and strength trends can add context. None proves muscle gain alone; review them with your weight trend before changing intake.
Run the loop automatically
Recomp AI brings your food log, weight trend and body measurements together. Review them alongside your training progress to decide whether your calorie target needs adjusting. Stable weight alone does not show whether you lost fat or gained muscle.
Body recomposition calculator questions
How does a body recomposition calculator work?
This calculator estimates maintenance or a 5 to 15 percent deficit, depending on body fat and training experience. It sets protein and projects fat and lean mass separately. These are starting estimates, not guaranteed outcomes. The calculator does not model the full range of calorie intakes at which recomposition may occur.
How should I set calories for recomposition?
Recomposition means losing fat and gaining muscle over the same period. Studies report fat loss with lean-mass gain during some deficits and around estimated maintenance, but lean-mass measurements do not isolate muscle. A slight surplus may also allow recomposition, yet evidence there is less direct: higher reported intake does not prove a measured surplus. This calculator selects maintenance or a 5 to 15 percent deficit, not the full possible range. No calorie target guarantees both changes.
How much protein does the calculator set?
About 2.2 g per kg of lean body mass as a daily floor. Anchoring to lean mass rather than total weight keeps the target honest at higher body fat. As a simpler rule of thumb, 1.6 to 2.2 g per kg of bodyweight works for most people.
Will the scale go down on a recomposition plan?
Weight may fall, stay similar or rise as fat, muscle, water and other tissue change. The calculator shows a modelled scenario, not a promised weight change. Compare your weight trend with body measurements and training progress. See the body recomposition guide for the full picture.
References
- Murphy C, Koehler K. Energy deficiency impairs resistance training gains in lean mass but not strength: A meta-analysis and meta-regression. Scand J Med Sci Sports, 2022;32(1):125-137.
- Antonio J, Ellerbroek A, et al. A high protein diet (3.4 g/kg/d) combined with a heavy resistance training program improves body composition in healthy trained men and women: a follow-up investigation. J Int Soc Sports Nutr, 2015;12:39.
- Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr, 1990.
- Helms ER, Aragon AA, Fitschen PJ. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. J Int Soc Sports Nutr, 2014.
- Morton RW, Murphy KT, 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. Br J Sports Med, 2018.
- Hall KD. What is the required energy deficit per unit weight loss? Int J Obes, 2008. (Tissue energy densities behind the fat-versus-muscle projection.)
- 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.
- Longland TM, Oikawa SY, et al. Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss. Am J Clin Nutr, 2016.
- Garthe I, Raastad T, et al. Effect of two different weight-loss rates on body composition and strength and power-related performance in elite athletes. Int J Sport Nutr Exerc Metab, 2011.