Cut fat without losing muscle. Build muscle without piling on fat. Both goals hinge on knowing your lean body mass.
Some calculations matter for a single decision; this one matters for years. Cut fat without losing muscle. Build muscle without piling on fat. Both goals hinge on knowing your lean body mass.
Lean body mass = total weight × (1 − body fat decimal). 80kg at 20% BF → 64kg LBM.
Protein needs, calorie targets, training volume all scale better with LBM than total weight.
Uses LBM directly: BMR = 370 + (21.6 × LBM kg). More accurate than Mifflin for lean individuals.
If weight drops but LBM stays steady, you're losing fat correctly. If LBM drops too, deficit is too aggressive.
Can I gain muscle and lose fat at the same time? Yes if you're a beginner, returning lifter, or have significant fat to lose. Advanced trainees need to pick a side.
Does cardio destroy muscle? Only excessive amounts. 3–4 sessions/week of moderate cardio is fine alongside lifting.
Run your own numbers before you trust a rule of thumb. Two minutes saves a lot of regret.