The Energetic Cost of Building Human Skeletal Muscle
Study Details
This paper developed a bottom-up model to estimate the energetic cost of building 1 kg of wet human skeletal muscle, including tissue energy, synthesis, deposition, maintenance and diet-induced thermogenesis 🔍
Here are the key points ⬇️
Key Findings
💪 1 kg of wet muscle was modelled as containing ~177 g protein, 30 g lipid and 20 g glycogen
🔥 The chemical energy stored in that new tissue was estimated at ~1355 kcal/kg
🧬 Adding the direct biochemical cost of synthesising protein, lipid and glycogen increased this to ~1515 kcal/kg
⚙️ Accounting for imperfect physiological deposition efficiency increased the requirement to ~2587 kcal/kg
🛌 Maintaining the accumulating muscle during a 12-week gain period added ~546 kcal/kg
🍽️ Including diet-induced thermogenesis produced a final central estimate of ~3481 kcal to build 1 kg of wet skeletal muscle
📊 The estimated range was ~3204–3710 kcal/kg, driven mainly by uncertainty around protein deposition efficiency
📅 If 1 kg of muscle was gained over 12 weeks, the tissue-specific requirement equated to only ~41 kcal/day
⚠️ This does NOT mean athletes should simply add 41 kcal/day, because training, recovery, other adaptations and errors in estimating maintenance needs are not included
📈 Common bulking recommendations of +300–500 kcal/day can create a surplus almost 10× greater than the estimated tissue-specific requirement
🩻 Larger surpluses may therefore increase fat gain without proportional increases in muscle gain
Conclusion
The energy required to physically build muscle itself may be relatively modest compared with traditional bulking surpluses 🧐
This estimate has not been directly measured in adults yet, therefore ~3500 kcal/kg should be viewed as a physiological reference point, not a prescribed calorie-surplus target ✅
Reference
https://www.biorxiv.org/content/10.64898/2026.08.17.745156v1.full
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