Accepted answer
More usefully, the mechanism is worth having straight, because it predicts which interventions can work and which cannot.
DEXA precision is better than people assume for fat mass and worse than people assume for lean mass in a single scan — the least significant change for regional lean mass on a well-maintained scanner is on the order of a few per cent. That means two scans three months apart can differ without anything having happened, and it means a scan sequence needs to be at least three points before a trend is interpretable.
Protein target arithmetic
| Body mass | 1.2 g/kg | 1.6 g/kg | 2.0 g/kg | Per meal at 1.6 (÷3) |
|---|
| 62 kg | 74 g | 99 g | 124 g | 33 g |
| 74 kg | 89 g | 118 g | 148 g | 39 g |
| 88 kg | 106 g | 141 g | 176 g | 47 g |
| 103 kg | 124 g | 165 g | 206 g | 55 g |
| 124 kg | 149 g | 198 g | 248 g | 66 g |
At roughly 4 kcal per gram, 141 g of protein is about 564 kcal — a substantial fraction of a 900 kcal budget, which is the real constraint.
Specifically, the regain trajectory after stopping is roughly a mirror of the loss trajectory, and it is not primarily a willpower phenomenon. Appetite signalling returns, energy expenditure remains suppressed relative to the original mass, and the two combine. That is an argument for a maintenance plan existing before the stop, rather than an argument against stopping.
The evidence for a higher protein intake preserving lean mass during an energy deficit is reasonably strong in resistance-trained populations and weaker in sedentary ones, with the meta-analytic estimates supporting intakes in the region of 1.6 g/kg over lower intakes when training is present[1].
One qualification: none of this is a clinical assessment, and unexplained loss of function rather than of mass is a reason to see someone rather than to adjust a programme.
Measure strength as well as mass. It is cheaper, it is less noisy, and it is closer to what you actually care about.