The keto diet takes carbohydrate very low — usually under 50 g a day — which forces the body to switch from burning glucose to burning fat, producing ketones for fuel. This metabolic state, called ketosis, is what defines the diet. It has a genuine medical pedigree in epilepsy, and for weight loss it works mainly by curbing appetite, with knock-on effects on blood sugar control and weight management.
What is the ketogenic diet?
Keto inverts the usual plate: roughly three-quarters of energy comes from fat, with moderate protein and very little carbohydrate. Cutting carbs below the body’s threshold depletes glycogen and shifts metabolism into ketosis within a few days. The catch is that it is demanding to maintain, and the fat sources you choose matter a great deal. You can read more on our keto diet hub.
What to eat on the keto diet
Meals are built from fatty and protein foods plus non-starchy vegetables: salmon, eggs, cheese and meat, with olive oil and other fats for cooking. Non-starchy vegetables such as spinach and broccoli supply fibre and micronutrients, while walnuts and other nuts add fat and crunch within the carb budget. Choosing unsaturated fats over a wall of processed meat is what protects the diet’s quality.
What to limit
Almost all carbohydrate-rich foods are out: grains, pulses, most fruit, starchy vegetables and anything with added sugar. That is a significant restriction — it removes many fibre- and nutrient-dense foods — so vegetables, nuts and seeds become important for keeping fibre and micronutrients up while staying in ketosis.
What the evidence says
The evidence is mixed and best described as moderate. It is strongest, and long-established, as a medical therapy for drug-resistant epilepsy. For weight loss, trials show it can be effective in the short term, largely through reduced appetite and calorie intake, with some benefit in selected cases of type 2 diabetes. Long-term cardiovascular effects, however, depend heavily on fat quality, and the research on lasting safety is still developing — so the usual disease-prevention claims should be treated cautiously.
Who it suits — and who should take care
Keto may suit people seeking short-term weight loss, those with drug-resistant epilepsy under specialist care, and some with type 2 diabetes — ideally with professional support. It is not a casual diet. Anyone who is pregnant, has type 1 diabetes, or has kidney, liver or pancreatic conditions should avoid it unless supervised, and people on diabetes or blood-pressure medication need medical guidance, as doses often have to change.
Common questions
Is the keto diet safe long term? The honest answer is that we don’t yet have strong long-term safety data, and the cardiovascular picture hinges on the type of fat eaten. Many people use keto as a short-term tool rather than a permanent diet, and medical supervision is wise for anyone staying on it.
What is the keto flu? In the first week, as the body adapts to ketosis, some people feel tired, headachy or foggy — often from fluid and electrolyte shifts. Staying hydrated and keeping up sodium, potassium and magnesium usually helps. If weight loss is the main goal, a gentler option like intermittent fasting may be easier to sustain.
