Body Recomposition Calculator

About Body Recomposition Calculator

How the Body Recomposition Calculator Works

The calculator runs through five steps to generate your targets:

1. BMR via Mifflin-St Jeor: Males = (10 x weight in kg) + (6.25 x height in cm) - (5 x age) + 5. Females = same formula but - 161 instead of + 5.
2. TDEE = BMR x activity multiplier (1.2 for sedentary up to 1.9 for extremely active)
3. Calorie target = TDEE adjusted for goal emphasis. Fat loss focus subtracts 300 cal, balanced subtracts 100 cal, muscle gain focus adds 100 cal.
4. Protein = lean body mass x protein multiplier (1.6g/kg for beginners, 2.0g/kg for intermediate, 2.2g/kg for advanced). Fat = 0.8g per kg of total body weight. Carbs fill the remaining calories.
5. Rest day adjustment = training day calories minus 200. Protein and fat stay constant; carbs are reduced.

Worked example: Male, 28 years old, 80 kg, 178 cm, 20% body fat, moderately active, intermediate lifter, balanced emphasis.

1. BMR: (10 x 80) + (6.25 x 178) - (5 x 28) + 5 = 1,777.5 cal
2. TDEE: 1,777.5 x 1.55 = 2,755 cal
3. Balanced target: 2,755 - 100 = 2,655 cal (training day), 2,455 cal (rest day)
4. Lean mass: 80 x 0.80 = 64 kg. Protein: 64 x 2.0 = 128g (512 cal). Fat: 80 x 0.8 = 64g (576 cal). Carbs: (2,655 - 512 - 576) / 4 = 392g
5. Rest day carbs: (2,455 - 512 - 576) / 4 = 342g

If you need to find your body fat percentage first, the Body Fat Calculator uses the US Navy method with just a tape measure.

Who Can Successfully Recomp?

Not everyone responds to body recomposition equally. Research from a 2020 systematic review in the Strength and Conditioning Journal (Barakat et al.) found that certain groups achieve meaningful simultaneous fat loss and muscle gain:

Group	Expected Results	Why
Training beginners (< 1 year)	Fastest recomp - up to 0.5-1 kg muscle/month	Untrained muscle is highly responsive to new stimulus ("newbie gains")
Returning lifters (after break)	Rapid regain due to muscle memory	Myonuclei remain in muscle fibres even after detraining, enabling faster regrowth
Higher body fat (men > 20%, women > 30%)	Good fat loss with modest muscle gain	More stored energy available, so the body can fuel muscle growth from fat reserves
Intermediate lifters (1-3 years)	Slower but measurable	Still have room for growth but rate of muscle gain has slowed
Advanced lifters (3+ years)	Very slow, near maintenance	Close to genetic ceiling for muscle mass, minimal untapped growth potential

Research by Hector and Phillips, who have published extensively on protein needs during energy restriction, has confirmed that a high protein intake (1.6-2.4 g/kg lean mass) combined with resistance training allowed subjects to gain lean mass while in a mild caloric deficit. The key was keeping the deficit small - around 100-300 calories below TDEE rather than the 500+ used in traditional cuts.

A landmark 2016 study by Longland et al. published in the American Journal of Clinical Nutrition put 40 young men on an aggressive 40% calorie deficit for four weeks. The high-protein group (2.4 g/kg/day) gained 1.2 kg of lean body mass while losing 4.8 kg of fat. The lower-protein group (1.2 g/kg/day) maintained lean mass but did not gain any. Both groups performed resistance training and high-intensity intervals six days per week. This study is one of the strongest demonstrations that protein intake is the deciding factor in whether recomp succeeds.

How Much Protein Does Recomp Actually Require?

Protein recommendations for recomp are based on lean body mass rather than total body weight. This is important because fat tissue does not need the same amino acid supply as muscle. Using lean mass gives a more accurate target, especially for people with higher body fat percentages.

Training Level	Protein per kg Lean Mass	Reasoning
Beginner (< 1 year)	1.6 g/kg	Newbie gains are driven more by neural adaptation than pure hypertrophy, so protein needs are slightly lower
Intermediate (1-3 years)	2.0 g/kg	Muscle protein synthesis response to training is lower than beginners, so dietary protein plays a bigger role
Advanced (3+ years)	2.2 g/kg	Near genetic ceiling - every marginal gain requires optimal nutrition and recovery

The International Society of Sports Nutrition (ISSN) position stand on protein and exercise (Jager et al., 2017) recommends 1.4-2.0 g/kg total body weight for most exercising individuals. For recomp specifically, the lean mass-based approach this calculator uses tends to produce similar numbers while being more precise for individuals outside average body fat ranges.

Distributing protein across 3-5 meals with at least 20-40g per sitting optimises muscle protein synthesis. Research by Schoenfeld and Aragon (2018) found that spreading protein intake supports a higher 24-hour muscle protein synthesis rate compared to concentrating it in one or two large meals.

Recomp vs Bulk and Cut

The traditional approach to changing body composition is cycling between bulking (caloric surplus for muscle gain) and cutting (caloric deficit for fat loss). Body recomposition offers a middle ground. Here is how they compare:

Factor	Body Recomp	Bulk then Cut
Calorie approach	Near maintenance (-300 to +100)	Surplus (+300 to +500) then deficit (-500 to -750)
Speed of muscle gain	Slower	Faster during bulk phase
Fat gain risk	Minimal	Moderate during bulk
Muscle loss risk	Minimal	Some during cut phase
Scale weight change	Little to none	Up during bulk, down during cut
Best for	Beginners, higher body fat, patience-focused	Intermediate to advanced lifters wanting faster progress
Psychological comfort	Easier - no extreme phases	Harder - surplus and deficit both have downsides
Timeframe	Ongoing, gradual	Typically 3-6 month cycles

For detailed macro splits tailored to specific goals, the Macro Calculator covers balanced, high-protein, low-carb, and keto profiles. If you want to understand your total daily burn in detail, the TDEE Calculator breaks it down step by step.

Common Recomp Mistakes and How to Avoid Them

Body recomposition requires patience and consistency. These are the most common mistakes that stall progress:

Mistake	Why It Hurts Progress	What to Do Instead
Eating too little protein	Without enough amino acids, muscle protein synthesis cannot outpace breakdown	Hit your protein target daily - it is the single most important macro for recomp
Creating too large a deficit	Aggressive deficits (500+ cal) shift the body toward catabolism, burning muscle for energy	Keep the deficit mild (100-300 cal) or eat at maintenance
Ignoring progressive overload	Without gradually increasing training stimulus, the body has no reason to build new muscle	Track your lifts and aim to increase weight, reps, or sets over time
Fixating on the scale	Body weight barely changes during recomp because fat loss and muscle gain offset each other	Track progress with photos, measurements, strength gains, and how clothes fit
Not sleeping enough	Growth hormone is released during deep sleep; poor sleep raises cortisol and impairs recovery	Aim for 7-9 hours per night
Skipping rest days entirely	Muscles grow during recovery, not during training	Take 2-3 rest days per week and reduce carbs on those days

Training and Rest Day Calorie Cycling

This calculator provides separate calorie targets for training and rest days. The logic is straightforward: on training days you burn more energy and need more fuel (particularly carbohydrates) to support performance and recovery. On rest days, energy demand is lower, so carbs are reduced by 200 calories while protein and fat stay the same.

A typical weekly structure for recomp might be 4 training days and 3 rest days. This means your weekly average calorie intake falls slightly below your training day target, creating a mild net deficit or near-maintenance intake depending on your goal emphasis setting.

The reason carbs are adjusted rather than protein or fat is practical. Protein needs to stay high to support muscle growth and recovery. Fat needs a minimum of roughly 0.8g per kg of body weight to maintain healthy hormone levels - testosterone, oestrogen, and other hormones involved in muscle building and fat metabolism are synthesised from dietary fat. Carbohydrates, while important for performance, are the most flexible macro and can be safely reduced on days with lower energy demand.

How to Track Recomp Progress

The biggest challenge with body recomposition is knowing if it is working, because the scale often stays flat. Fat is being lost and muscle is being gained, but since muscle is denser than fat, your weight may not change even though your body is visibly different.

Tracking Method	Frequency	What It Tells You
Progress photos (front, side, back)	Every 2-4 weeks, same lighting and time of day	Visual changes that the mirror and scale miss
Body measurements (waist, chest, arms, thighs)	Every 2-4 weeks	Waist shrinking + arms/chest growing = recomp working
Strength log	Every session	If lifts are going up over time, muscle is likely being built
Body fat calipers or scans	Every 4-8 weeks	Direct measurement of fat vs lean tissue change
How clothes fit	Ongoing	Looser waistband + tighter sleeves is the classic recomp indicator
Scale weight	Weekly average (not daily)	Mainly useful to confirm weight is stable rather than trending sharply in either direction

Give recomp at least 8-12 weeks before judging results. Body composition changes are slower than pure weight loss or weight gain, and short-term water fluctuations can mask real progress. Take photos in the same conditions each time for the most reliable comparison.

For a protein-focused deep dive including food sources and timing, the Protein Calculator provides more detailed recommendations by activity type.

All calculations run entirely in your browser. No personal data is sent to any server.

Sources

• Longland et al. (2016) - Higher compared with lower dietary protein during energy deficit - American Journal of Clinical Nutrition
• Barakat et al. (2020) - Body Recomposition: Can Trained Individuals Build Muscle and Lose Fat - Strength and Conditioning Journal
• Jager et al. (2017) - ISSN Position Stand: Protein and Exercise
• Schoenfeld and Aragon (2018) - How much protein can the body use in a single meal for muscle-building
• Mifflin et al. (1990) - A new predictive equation for resting energy expenditure
• NHS - Strength and Flexibility Exercise Guidelines