The reasoning: the insulin–glucagon ratio sets the fuel mode
| Tissue | Insulin (fed) | Glucagon (fasting) |
|---|---|---|
| Liver | ↑ glycogen synthesis, glycolysis, lipogenesis; ↓ gluconeogenesis, glycogenolysis, ketogenesis (no GLUT4 needed) | ↑ glycogenolysis, gluconeogenesis, ketogenesis (cAMP; ↓ malonyl‑CoA → CPT‑1 disinhibited) |
| Muscle | ↑ GLUT4 glucose uptake, glycogen, protein synthesis | no direct effect (no glucagon receptors) |
| Adipose | ↑ GLUT4 uptake, LPL, fat storage; ↓ hormone‑sensitive lipase | (lipolysis driven mainly by low insulin + catecholamines) |
| Potassium | ↑ Na⁺/K⁺‑ATPase → K⁺ into cells | — |