The ketogenic diet sits at around 70 to 80 percent of energy from fat, 15 to 25 percent protein, and under 50 g of carbohydrate per day. The original clinical use was paediatric epilepsy and there is strong evidence for that indication. The popular weight loss and metabolic versions have a more mixed evidence base. The mechanism is real. The tradeoffs are real too.
The mechanism
When carbohydrate intake stays under about 50 g a day, the liver converts fatty acids into ketone bodies (beta-hydroxybutyrate, acetoacetate, acetone). Most cells then use ketones as their primary fuel. Insulin sits very low. Fat oxidation is high. Hunger often drops, partly through ketone effects on hypothalamic signalling and partly through high protein at every meal.
What the evidence supports
- Drug-resistant paediatric epilepsy. Established clinical use under NHS specialist care.
- Short-term weight loss. Equivalent to low-fat diets at 6 to 12 months when calories are matched. Faster initial loss largely from glycogen and water.
- Type 2 diabetes management. Improvements in HbA1c and medication needs seen in short-term trials. NICE notes evidence is still evolving; the Diabetes UK position recognises low-carb as one acceptable option under clinician supervision.
Trade-offs
- Adherence is hard. Drop-out rates are higher than less restrictive approaches in long-term trials.
- LDL cholesterol rises in a subset of people on the same diet ("lean mass hyper-responder" phenotype).
- Athletic performance for short, high-intensity work (sprints, repeated efforts under 90 seconds) can drop, at least in the first 6 to 12 weeks.
- Lower intake of whole grains, fruit, and legumes restricts fibre and micronutrient diversity.
Who should not try keto without medical input
- Type 1 diabetes (risk of ketoacidosis).
- Pregnancy and breastfeeding.
- Known kidney disease, gallstones, or pancreatitis history.
- History of disordered eating.
- Adults on insulin or sulfonylureas without prescriber adjustment.
For a sustainable nutrition plan with the diet style that fits your life, book a consultation at www.dushyantatomar.com.
Dushyanta Tomar, MSc Applied Sports and Exercise Physiology, CIMSPA Accredited Personal Trainer.
Sources
- Bueno NB, de Melo IS, de Oliveira SL, da Rocha Ataide T. Very-low-carbohydrate ketogenic diet v. low-fat diet for long-term weight loss: meta-analysis of randomised controlled trials. Br J Nutr. 2013, vol 110, issue 7, pages 1178 to 1187.
- Kossoff EH, Zupec-Kania BA, Auvin S, et al. Optimal clinical management of children receiving dietary therapies for epilepsy: updated recommendations. Epilepsia Open. 2018, vol 3, issue 2, pages 175 to 192.
- Diabetes UK. Low-carb diet position statement. diabetes.org.uk