Ketogenic diet
What it is
A diet with carbohydrate held below the level at which the body switches to producing ketones from fat as a major fuel — nutritional ketosis. The definition this site uses puts the threshold at under about 50 grams of carbohydrate a day, or under ten percent of energy; that is the number from the published definition, not an engineering guess, and it is the line that separates "ketogenic" from merely low-carbohydrate (under 130 grams or 26 percent). Fat becomes most of the energy by default, because something has to; protein stays moderate, because a great deal of it is turned into glucose and can blunt ketosis.
How it works in practice
Meat, fish, eggs, cheese, oils, nuts and seeds, non-starchy vegetables, small amounts of berries. No bread, pasta, rice, potatoes, sugar, most fruit, beer. The first week is where most of the experience happens: glycogen is used up and the water bound to it leaves — two or three kilograms on the scale that are not fat — and many people report tiredness, headache and cramps as the body adapts and as sodium, potassium and magnesium go out with the water. Salt and fluids ease most of it. After that, appetite is often lower than on other patterns, which is the practical mechanism by which people hold a deficit on it.
What the evidence shows
The network meta-analysis of named dietary programmes found low-carbohydrate programmes losing roughly four to five kilograms more than usual diet at six months — about the same as low-fat programmes — and at twelve months the differences between named diets had shrunk to small and mostly non-significant amounts, with low certainty. The Cochrane review of low-carbohydrate against balanced-carbohydrate diets reaches the same place: little to no difference in weight at up to two years. A 2024 review of the ketogenic meta-analyses adds the methodological caveat that matters most here: ketosis is rarely verified in the trials, dropout is high, and "ketogenic" often means "was assigned to". The honest reading is that the pattern works as well as the deficit it produces, starts faster on the scale, and shows no advantage that survives a year.
Who it tends to suit
People who find carbohydrate the food they cannot stop eating, and for whom the blunted appetite is worth the loss of bread. People who cook, and who eat mostly at home. People without the medical conditions below, and without a history of restriction-and-binge.
How it most often fails
Socially, at the table — the pattern is visible at every meal and every celebration, and it is the one most often abandoned at a wedding. Nutritionally, in fibre: vegetables have to be deliberate, or the diet becomes meat and cheese. And on the scale in reverse: the first carbohydrate meal after weeks of ketosis restores glycogen and its water, and the two kilograms that "came back overnight" are the same two that left in week one.
What to watch
Electrolytes in the first weeks — salt is not the enemy here — and fibre throughout. Anyone on diabetes medication needs a doctor before starting, not after: insulin and sulfonylurea needs fall quickly, and SGLT2 inhibitors carry a specific ketoacidosis risk on this pattern.
In the app
The app knows the ketogenic policy code and treats it as a preference the planner takes into account; it does not verify the carbohydrate threshold or ketosis, because that policy revision has no documented review yet. The site says the same thing, and will change the wording the day the app can verify the rule.