How much muscle can I gain in a year?
Roughly 4 to 7 kg in a good first year for men and half that for women, then less every year after.
No trial follows untrained people for a year, so this is extrapolation from shorter studies rather than a measured figure. What those studies agree on is the shape: fastest at the start, slower every block after, and roughly half the rate for women because they start with less testosterone, not less potential.
A rough ladder for men: 4 to 7 kg in year one, 2 to 3 kg in year two, 1 to 2 kg in year three, and after that you are fighting for a kilo. Halve those numbers for women. The ceiling is real as well: drug-free lifters rarely pass a fat free mass index of about 25, which for a 180 cm man is around 81 kg of lean mass.
Anything promising 10 kg of muscle in twelve weeks is selling you water, glycogen and fat.
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- Morton, R.W. et al. (2018). A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med 52(6). 49 trials, 1,863 people: training added fat free mass over weeks to months, and extra protein added only 0.3 kg on top of that.
- Damas, F. et al. (2018). The development of skeletal muscle hypertrophy through resistance training: the role of muscle damage and muscle protein synthesis. Eur J Appl Physiol 118(3). Real growth only becomes measurable after about 18 sessions; the first weeks are mostly swelling from damage.
- Kouri, E.M. et al. (1995). Fat-free mass index in users and nonusers of anabolic-androgenic steroids. Clin J Sport Med 5(4). Where the ceiling sits: drug-free lifters clustered around a fat free mass index of 25.