A healthy body knows two fuels: carbohydrates when they are available, and fat when they are not—and switches between them overnight without asking. A body running on sugar six times a day has forgotten the second option: without food for three hours—shaking, hunger, brain fog, because fat as fuel is blocked by insulin and the sugar has run out. “I can’t go without snacks” is not character, but lost flexibility. It returns in two to four weeks. The main page on the topic is metabolic health.
2-4 weeks
until flexibility returns
0,5-3
mmol/L of ketones — nutritional ketosis
2-3 h
after eating — a crash in inflexible people
3 out of 5
criteria — metabolic syndrome
The switch is insulin. High insulin— the body burns carbohydrates and stores fat; access to reserves is closed. Low insulin—access is open, and fat becomes fuel. With frequent carbohydrates, insulin is always high, and the switch has rusted: even with low blood sugar, the body cannot access fat, hence hunger after two hours and “I’ll faint without lunch.” Low-carbohydrate eating and pauses remove the rust: after 2-4 weeks, switching works again, and 14-16 hours without food pass unnoticed. Read more about metabolic flexibility.
When fat burns quickly, the liver makes ketones from it—fuel for the brain, which cannot consume fat directly. Blood ketones of 0.5-3 mmol/L mean nutritional ketosis, a normal state of the body without carbohydrates; this is not diabetic ketoacidosis at 15-25, a tenfold difference. Measuring ketones is not necessary: if hunger between meals has disappeared and energy is steady, the switch has occurred. “Chasing ketones” is a mistake; they are an indicator, not the result. Read more about ketones without the mystique.
| Sign | No flexibility | Present |
|---|---|---|
| After 3-4 hours without food | shaking, hunger, brain fog | steady, can last 6 hours |
| Morning without breakfast | impossible | fine until 11-12 |
| After eating | sleepiness, crash | steady energy |
| Fasted workout | darkening vision | goes normally |
| Craving sweets | daily | rarely or never |
| Sleep | waking from hunger | steady |
Lunch—and an hour later you are so sleepy that you cannot work. This is not “overeating,” but a roller coaster: blood sugar rises, insulin overshoots, blood sugar falls below normal—reactive hypoglycemia. The more carbohydrates in the meal, the deeper the crash. An omelet with salad does not cause a crash. Circadian rhythms also play a role—everyone experiences an afternoon decline in alertness, but the roller coaster turns it into near-fainting. Read more about energy crashes after meals.
Five criteria; three out of five mean the syndrome: waist circumference from 80 cm in women, triglycerides from 1.7, HDL below 1.3, blood pressure from 130/85, fasting glucose from 5.6. Two numbers at home, three in a laboratory, one visit. The syndrome is not a lifelong diagnosis, but a list of issues fixed by the same lever. For most people, after 3-6 months of the method, the number of criteria falls to zero or one. Read the explanation and download the form at metabolic syndrome checklist.
| Days | What you feel | What is happening | What to do |
|---|---|---|---|
| 1-3 | headache, weakness, irritability | insulin has dropped, the kidneys are excreting sodium and water | salt 3-5 g, water 2-3 L, magnesium — this is not hunger |
| 4-10 | lower training performance, craving sweets | fat-burning enzymes are waking up, ketones are appearing | do not quit, 12/12-14/10 window, walking |
| 10-21 | hunger between meals disappears | the switch is working, energy is steadier | 14/10 — 16/8 window, strength training |
| 21-30 | 16/8 feels effortless, fasted training works | flexibility has returned | maintain; berries and vegetables do not disrupt it |
The first two weeks are difficult, then the switch turns on. Do not quit on day 10.
Hunger is gone, energy is steady—the switch is working. No strips are needed.
Without them, the transition looks like an illness. The body is not “unable”; it is sodium.
The checklist is the starting point. Recount after six months.
“I can’t fast for 16 hours” and “I can’t go without snacks” are the same statement. Not because the window is long, but because the switch to fat is not working: without sugar, the body cannot access fuel from its reserves and panics. That is why the method follows this order: first, a low-carbohydrate plate for two to three weeks—the switch is repaired—and only then extend the window to 14/10 and 16/8, which by that point feel effortless. Those who start with 16/8 while eating carbohydrates suffer, break down, and decide that “fasting is not for me.” It is not fasting, but the order. Basics: intermittent fasting; getting started: how to start fasting.
Nutritional ketosis 0.5-3 mmol/L — no, this is the physiology of going without carbohydrates. Ketoacidosis — 15+ with type 1 diabetes without insulin, a different condition.
2-4 weeks. The first 3-5 days — electrolytes, up to 2 weeks — lower strength, then steady. After a month — easier than it was on carbohydrates.
Yes, in a few weeks on sugar six times a day. And regain it again faster. The method is not a course, but a way of eating.
Waist, triglycerides, HDL, blood pressure, glucose. Three out of five — syndrome, and weight has nothing to do with it. How to check yourself, what each item means, and why after six months of the method they are usually zero.
Lunch — and an hour later you can't work. It's not that you "overate"; it's a roller coaster: blood sugar rises, insulin overshoots, and blood sugar drops below normal. Reactive hypoglycemia, the afternoon slump, and how to eat so you have energy after a meal.
A healthy body switches from carbohydrates to fat overnight. A body fueled by sugar six times a day has forgotten how: without food for three hours — shaking and brain fog. It’s not character, but a rusty switch, and it can be fixed in a month.
When fat burns quickly, the liver turns it into ketones — fuel for the brain. 0,5-3 mmol/L is normal without carbohydrates, not ketoacidosis. What they mean, how to measure them, and why strips aren't needed.
Reviewed by Anastasia Zhukova, Fitness Trainer • Author of a Nutrition and Training System • Creator of an AI Personal Support Platform
A human has reviewed this material against the method and real client practice.
