The fed and fasted states as `cif01` frames them — and what the primaries here do and do not establish about the switch between them.
What the evidence says
- Fed state, on `cif01`’s account: insulin elevated, body prioritises storing incoming energy, uses glucose for fuel[1]
- Fasted state, on the same account: insulin low, body shifts to burning stored fat, ketone production begins[1]
- Fasting-dependent switch from glucose-driven oxidative phosphorylation to ketone body and fatty acid-dependent metabolism[2]
- Upon >24 hours of fasting, humans enter alternative metabolic phases relying on ketone body-like carbon sources[2]
- Respiratory quotient fell from 0.83 (day 1) to 0.71 (day 4) during fasting, quantifying the shift from glucose to fat oxidation[3]