Metabolic flexibility: why some can go 16 hours without eating while others «crash» after three

You eat carbohydrates — insulin rises — the body burns glucose and closes access to fat. 3-4 hours pass — insulin falls — the body opens access to fat and switches to it. Overnight — on fat, breakfast — back again. In a flexible body, these transitions are unnoticeable. The problem: with frequent carbohydrates, insulin does not have time to fall — access to fat is always closed, and the enzymes that burn it «sleep» because they are not needed. Sugar runs out — fat is unavailable — panic: shaking, hunger, brain fog, anger. This is exactly «can’t go without snacks».

Days 1-3: without sugar and flour, insulin falls, the kidneys release water and sodium — headache, weakness; this is salt and water, not hunger. Days 4-10: fat-burning enzymes wake up, ketones appear, workout performance is slightly lower. Days 10-21: hunger between meals disappears, the 14/10 window passes unnoticed, energy is steadier than on carbohydrates. Week 4+: 16/8 without effort, fasted workouts are manageable, cravings for sweets are rare. Whoever quits on day 5 has not reached the switch. Ketones as an indicator — ketones without mysticism, salt — salt on a low-carb diet.