Atkins
What it is
The commercial programme that made low-carbohydrate eating famous, built around phases: a two-week induction at about twenty grams of carbohydrate a day — ketogenic by the published definition — then carbohydrate added back in steps of a few grams a week until weight loss slows, then a maintenance level at the highest carbohydrate the person can hold their weight on. Meat, eggs, cheese, fish and low-carbohydrate vegetables throughout; the branded bars and shakes are optional and, in Bulgaria, mostly unavailable.
How it works in practice
The induction phase is the ketogenic diet for two weeks, with its fast start and its adaptation symptoms. After that the programme is a lower-carbohydrate diet with a built-in method for finding your own carbohydrate level — which is its one genuinely useful idea, and the one people most often skip by staying in induction indefinitely.
What the evidence shows
In the network meta-analysis of named dietary programmes, Atkins was among those with the largest weight loss at six months — on the order of five kilograms more than usual diet, with moderate certainty — and at twelve months the differences between named diets had shrunk to small, mostly non-significant amounts with low certainty. That is the pattern for every low-carbohydrate programme in the review, and the lower-carbohydrate page has the head-to-head trials that explain it: the deficit does the work, the first weeks' water flatters the rate, and the year evens things out.
Who it tends to suit
The same people as the ketogenic and lower-carbohydrate patterns — those for whom carbohydrate is the food they cannot stop eating — with the added appeal of a structure that tells them what to do next.
How it most often fails
By never leaving induction, which turns a phased programme into an indefinite ketogenic diet that few people keep; by the branded products, which are processed food in low-carbohydrate packaging; and socially, at the table, like every low-carbohydrate pattern.
What to watch
Fibre and electrolytes during induction; the step-up phases, done honestly rather than skipped; and, for anyone on diabetes medication, a doctor before the induction phase, not after.
In the app
The app has policy codes for the two levels the programme moves between — lower-carb and ketogenic — but no phased programme, so Atkins as such is not something the planner schedules or verifies.