Ketosis

Ketosis is a metabolic state in which the body uses ketone bodies as a major source of energy due to limited carbohydrate availability or prolonged energy deficit. It commonly occurs during fasting, prolonged exercise, or very low-carbohydrate diets. Ketone bodies produced by the liver include acetoacetate, beta-hydroxybutyrate, and acetone, which circulate in the blood and can be used by most tissues, including the brain.

Physiologically, when glucose is scarce, insulin levels fall and fatty acids are released from adipose tissue. The liver converts these fatty acids into acetyl-CoA and then into ketone bodies through ketogenesis. Ketone bodies provide an alternative energy source for peripheral tissues and can cross the blood-brain barrier to supply the brain when glucose is limited.

Biomarkers and diagnosis depend on measurement. Nutritional or fasting ketosis typically yields blood ketone levels around 0.5 to 3.0 mmol/L. Urine ketones detect acetoacetate, while breath tests can reflect acetone. Ketosis must be distinguished from ketoacidosis, a dangerous condition marked by very high ketone levels and metabolic acidosis, most commonly associated with uncontrolled diabetes or alcohol-related states.

Causes and dietary context include fasting, extended exercise, and deliberate restriction of carbohydrates. The ketogenic diet is a therapeutic, medically supervised diet that induces ketosis by restricting carbohydrate intake and increasing fats, sometimes with higher protein in targeted variants. It is used clinically for drug-resistant epilepsy and is being studied for obesity, type 2 diabetes, metabolic syndrome, and certain neurological disorders.

Safety and limitations: ketosis is generally safe for healthy individuals under guidance, but possible side effects include dehydration, electrolyte imbalance, and gastrointestinal issues. Ketoacidosis remains a medical emergency requiring urgent care.