Body stages Stage 8 of 11
Protein-sparing adaptation
The body shifts to protect muscle: ketones reduce protein breakdown. Much of the early lean-mass drop is water, largely regained after eating.
In Nesteia. Reached at 72 hours, on any fast that passes it. The 96 and 120‑hour plans run only for people fasting under a clinician, confirmed before every such fast.
What studies measured
Ketones suppress nitrogen loss; early lean loss is mostly water and largely regained in 3 days.
How it may feel
Energy is often steady; cold hands and lighter sleep are common.
What to do
Supervised plans only. Keep fluids and sodium up, stand slowly, and follow your clinician's monitoring plan.
Sources
- Owen 1998Protein, fat, and carbohydrate requirements during starvation: anaplerosis and cataplerosis. Am J Clin Nutr, 1998.
- Felig 1969Amino acid metabolism during prolonged starvation. J Clin Invest, 1969.
- Pietzner 2024Systemic proteome adaptions to 7-day complete caloric restriction in humans. Nat Metab, 2024.
What studies measured in healthy adults, not a reading of your own body. Stop and seek help if you feel unwell; the signs to stop for are listed under Stop signs on the safety page.