Ketosis

Ketosis occurs when the body's carbohydrate stores are depleted and it switches to burning fat as its primary fuel source. The liver converts fatty acids into ketone bodies, which can be used by the brain, heart, and muscles for energy in place of glucose. This metabolic shift typically occurs after two to four days of consuming fewer than 20 to 50 grams of carbohydrates per day.

The ketogenic diet deliberately induces nutritional ketosis for weight loss, blood sugar management, and other health benefits. Research has shown that ketogenic diets can be effective for rapid weight loss, improving insulin sensitivity, reducing triglycerides, and increasing HDL cholesterol. Some studies suggest benefits for neurological conditions including epilepsy, where ketogenic diets have been used therapeutically since the 1920s.

Ketosis is different from ketoacidosis, a dangerous condition occurring primarily in people with type 1 diabetes where ketone levels become dangerously high alongside elevated blood sugar. Nutritional ketosis produces moderate, controlled ketone levels between 0.5 and 3.0 mmol/L, while ketoacidosis involves levels above 10 mmol/L. Common side effects during the initial transition to ketosis include fatigue, headache, and irritability, often called the keto flu.