What Is Ketosis?
Ketosis is a metabolic state in which your body burns fat and ketone bodies as its primary fuel instead of glucose. It's triggered by drastically reducing carbohydrate intake β typically to 20β50 g per day on a ketogenic diet. When liver glycogen stores (roughly 100β120 g) are depleted, the liver begins converting fatty acids into ketone bodies: acetoacetate, beta-hydroxybutyrate (BHB), and acetone.
Full fat adaptation β where your body efficiently uses fat at high intensity β takes 3 to 12 weeks after entering ketosis. During the first 1β2 weeks, many people experience keto flu driven by water and electrolyte loss. Staying on top of sodium (3β5 g/day), magnesium (300β500 mg), and potassium (1β3 g) makes this period much more manageable.
Phase-by-Phase Tips
- Days 1β4: Glycogen depletes β drink water aggressively and add salt to meals
- Week 1β2: Keto flu window β prioritize electrolytes; fatigue and brain fog are temporary
- Weeks 3β6: Fat adaptation β athletic performance dips then recovers; energy stabilizes
- After 6 weeks: Full adaptation β sustained energy, stable appetite, improved mental clarity
Frequently Asked Questions
A blood ketone meter reading of 0.5β3.0 mmol/L (BHB) confirms nutritional ketosis. Urine strips and breath meters work but are less accurate over time. Fruity breath and reduced hunger are common early signs.
Keto flu includes fatigue, headaches, muscle cramps, and brain fog that appear in the first 1β2 weeks of carb restriction. It's caused by electrolyte loss as glycogen depletes. Replenishing sodium, magnesium, and potassium solves it in most cases.
Yes β regular exercise depletes glycogen faster, cutting 1β2 days off your timeline. Just don't refuel with carbs after training, or you'll reset the clock.