Ketogenic diet and brain health: how the brain uses ketones

For many years we treated the brain and body as if they were separate. We now know they communicate constantly—through nerves, hormones, immune signals, and a selective blood–brain barrier that is far more dynamic than once thought.

A major clinical bridge came from ketogenic therapy in epilepsy, led by Prof Helen Cross OBE (Great Ormond Street Hospital) and Prof Eric Kossoff (Johns Hopkins). Their work helped change epilepsy care worldwide and inspired further exploration of metabolic approaches in psychiatry, such as Prof Chris Palmer to look at using the Keto diet to manage bipolar and schizophrenia. The work of Dr Bredesen was also based on the amazing success of the epilepsy research.

The gut–brain axis adds another layer: diet quality, fibre, and microbial metabolites shape inflammation and neurotransmission. Evidence suggests responses are individual—some people do well on lower-carbohydrate, higher-fat patterns (including ketogenic variants), others on more moderate approaches. The common thread is better metabolic control.

Why “fat for fuel” can help the brain
When carbohydrate intake is lower and insulin falls, the liver produces ketone bodies (β-hydroxybutyrate, acetoacetate). The brain can use these ketones as an efficient alternative fuel, which may help bypass impaired glucose use, stabilise neuronal excitability, and support mitochondrial/redox function. Insulin still responds to protein and, to a lesser extent, fat, but typically far less than to carbohydrate—so energy delivery can feel steadier.

What switching fuels actually looks like

1. Blood glucose stabilises as carbohydrate intake is reduced.
2. In the first few days you may feel tired/headachy (“keto-flu”) while fat pathways up-regulate—hydration and electrolytes (sodium, potassium, magnesium) make this transition much smoother.
3. At 12–36 hours: ketone levels begin to rise; over days to weeks, enzymes for ketone use increase. The liver supplies fatty acids (from diet and stores) to tissues, where they are converted to adenosine triphosphate (ATP), the body’s main form of energy.
4. Many people notice more stable energy (fewer peaks/troughs) as fat and ketones provide a steadier supply, with the brain able to use ketones when glucose handling is sub-optimal.

Try this week

• Protein-first meals: build plates around eggs, fish, meat, tofu/tempeh; add non-starchy veg and olive oil/avocado/nuts.
• Post-meal walk: 10–15 minutes after your main meals to smooth glucose swings.
• Hydrate well: Plenty of fluid and add a pinch of mineral salt or electrolyte drops if you’re reducing carbs.

If you use insulin or sodium-glucose co-transporter 2 (SGLT2) inhibitors, are pregnant/breastfeeding, have a history of eating disorders, pancreatitis, or a known fat-oxidation disorder, please discuss dietary changes with your clinician first. Most others can trial a gentle reduction in refined carbohydrates while focusing on real food and adequate protein.