What Is Lean Body Mass?
Lean Body Mass (LBM) is everything in your body except fat — muscles, bones, organs, connective tissue, blood, and water. It is a far better predictor of metabolic rate, strength, and health than total body weight. Two people can weigh the same but have drastically different LBM values.
Boer Formula for LBM
Men: LBM = (0.407 × weight kg) + (0.267 × height cm) − 19.2
Women: LBM = (0.252 × weight kg) + (0.473 × height cm) − 48.3
Women: LBM = (0.252 × weight kg) + (0.473 × height cm) − 48.3
Why LBM Matters
- Metabolic rate: Each kg of muscle burns ~13 kcal/day at rest vs ~4 kcal/day for fat
- Drug dosing: Many medications (e.g. for anaesthesia, antibiotics) are dosed by LBM not total weight
- Fitness tracking: LBM tells you if you're building muscle or just gaining fat during bulking
- Weight loss: Protecting LBM during a caloric deficit requires adequate protein and resistance training
How to Increase Lean Body Mass
- Resistance training 3–5 times per week using progressive overload
- Eat 1.6–2.2g of protein per kg of body weight daily
- Ensure caloric surplus or maintenance (not deficit) for muscle building
- Prioritise sleep — growth hormone peaks during deep sleep