Ketogenic Diet

What the ketogenic diet actually does to your body

The ketogenic diet is a high-fat, very low-carbohydrate eating pattern that forces a metabolic shift from glucose burning to fat burning. By cutting carbohydrates below roughly 50 grams per day, you deplete liver glycogen and push your body into ketosis, a state where the liver converts fatty acids into ketone bodies (beta-hydroxybutyrate, acetoacetate, and acetone). These ketones then supply 60-70% of the brain's energy and become the primary fuel for muscles and the heart. The diet typically follows a macronutrient ratio of about 70-75% fat, 20-25% protein, and 5-10% carbohydrate by calories.

The ketogenic diet was first developed in the 1920s to treat drug-resistant epilepsy in children, and it remains a standard clinical therapy for seizure disorders today ^[1]. Over the past decade, interest has expanded into weight management, type 2 diabetes, and even longevity research.

Ketogenic diet and longevity: what the research shows

Two landmark 2017 studies in mice showed that a ketogenic diet extended median lifespan by 13.6%, preserved muscle mass, and improved memory in aging animals ^[2][3]. The mice on a ketogenic diet maintained grip strength and showed increased mitochondrial biogenesis in skeletal muscle, with a shift toward more oxidative muscle fiber types. A 2024 retrospective analysis of over 43,000 human adults found that a higher dietary ketogenic ratio was inversely associated with all-cause mortality, without increasing cardiovascular-related deaths ^[4].

The longevity mechanism likely involves beta-hydroxybutyrate (BHB), the primary ketone body. BHB inhibits the NLRP3 inflammasome (reducing chronic inflammation), acts as a histone deacetylase inhibitor (affecting gene expression), and activates antioxidant pathways. These properties make it more than just a fuel molecule.

Metabolic benefits: weight loss and blood sugar control

An umbrella review of 23 meta-analyses found high-quality evidence that the ketogenic diet reduces triglycerides and seizure frequency, with moderate-quality evidence for decreasing body weight, HbA1c, and respiratory exchange ratio ^[5]. For type 2 diabetes specifically, a systematic review found average fasting glucose reductions of 1.29 mmol/L and HbA1c reductions of 1.07% compared to control diets ^[6]. Weight loss effects are significant in the short to medium term, with studies documenting average reductions of 9.13 kg in body weight.

The weight loss mechanisms go beyond simple calorie reduction. Ketosis suppresses ghrelin (the hunger hormone), increases satiety from higher fat and protein intake, and raises the metabolic cost of converting fat to usable energy. Many people find they eat less without consciously restricting calories.

Risks and trade-offs you should know about

The ketogenic diet is not without downsides. During the first week, many people experience "keto flu" with fatigue, headaches, and irritability as electrolytes shift. Supplementing sodium, potassium, and magnesium helps. The bigger concern is long-term. The diet consistently raises LDL cholesterol, sometimes dramatically: one case series found average LDL levels of 316 mg/dL in long-term keto dieters, with some exceeding 800 mg/dL ^[7]. While a 2024 trial found that diet-induced LDL elevation didn't correlate with increased coronary plaque in metabolically healthy individuals, this remains an active area of debate.

Other documented long-term risks include kidney stones, constipation from low fiber intake, potential nutrient deficiencies (B vitamins, magnesium, zinc), and in animal studies, impaired glucose tolerance after reintroduction of carbohydrates. People with liver disease, pancreatic conditions, or a history of eating disorders should avoid the diet entirely.

Practical implementation and who it's best suited for

Reaching ketosis takes 3-7 days of strict carb restriction. You can verify ketosis with urine strips, breath analyzers, or blood ketone meters (the most accurate option, targeting 0.5-3.0 mmol/L BHB). Focus on quality fats: olive oil, avocados, nuts, fatty fish, and eggs rather than processed meats and excessive saturated fat. Include plenty of non-starchy vegetables for fiber and micronutrients.

The strongest evidence supports ketogenic diets for drug-resistant epilepsy, short-to-medium term weight loss, and glycemic control in type 2 diabetes under medical supervision. For longevity, the animal data is promising but human trials are still lacking. Cycling in and out of ketosis (periodic ketogenic eating rather than permanent adherence) may offer a practical middle ground that captures metabolic benefits while reducing long-term risks. Regular blood work, especially lipid panels, is non-negotiable for anyone on this diet long-term.