Ketosis

In 1921, endocrinologist Rollin Woodyatt observed that starvation and low-carb diets produced the same chemical environment in the body, leading Mayo Clinic physician Russell Wilder to coin the term "ketogenic diet" as an epilepsy treatment. For children with drug-resistant epilepsy, ketosis can reduce seizures by 50-90%, though doctors still don't fully understand why. This therapeutic application predates modern diet trends by nearly a century, and remains one of the most evidence-backed medical uses of intentional ketosis today.

While glucose is often called the brain's "only" fuel, ketone bodies can supply up to 70% of the brain's energy needs during prolonged fasting or carbohydrate restriction. This metabolic flexibility likely kept our ancestors cognitively sharp during seasonal food scarcity, contradicting the myth that you need constant carbs to think clearly. Some research suggests ketones burn more efficiently than glucose, producing fewer damaging free radicals per unit of energy—though the jury's still out on whether this translates to measurable cognitive benefits in healthy adults.

One unmistakable sign of ketosis is breath that smells fruity or like nail polish remover, caused by acetone—a ketone body your lungs excrete. Ancient physicians actually diagnosed diabetes by tasting patients' urine for sweetness, but they were also unknowingly detecting ketones in cases of diabetic ketoacidosis. Today's biohackers use breath meters or urine strips to track ketosis, turning this metabolic byproduct into a measurable data point for optimization.

Traditional Inuit populations thrived on diets consisting of 70-80% fat with almost no plant foods, yet they weren't in continuous ketosis like modern keto dieters. Their bodies adapted to produce glucose from protein through gluconeogenesis, and they likely cycled in and out of ketosis seasonally. This challenges simplistic narratives about "ancestral" ketogenic diets and reveals that human metabolism is remarkably adaptable rather than requiring one optimal fuel state.

Transitioning into ketosis often triggers a cluster of symptoms—headaches, fatigue, irritability, and brain fog—dubbed the "keto flu," which is really your body staging a metabolic rebellion against sudden carb withdrawal. The discomfort stems from electrolyte imbalances (especially sodium and magnesium depletion) and your cells' slow adaptation to burning fat efficiently, typically lasting 3-7 days. Counterintuitively, adding more salt and fluids during this transition, not toughing it out, makes the adaptation smoother and faster.

Nutritional ketosis (ketone levels of 0.5-3.0 mmol/L) is vastly different from diabetic ketoacidosis (often above 10 mmol/L), a life-threatening condition almost exclusive to type 1 diabetics whose lack of insulin allows both glucose and ketones to skyrocket simultaneously. This crucial distinction is often lost in public discourse, leading to confusion where doctors warn against ketosis generally based on ketoacidosis, while diet proponents dismiss all concerns. Understanding this spectrum—from therapeutic to dangerous—is essential for anyone experimenting with metabolic interventions.