There are four phases of the Atkins diet: induction, ongoing weight loss, pre-maintenance and lifetime maintenance.
The Induction phase is the first, and most restrictive, phase of the Atkins Nutritional Approach. It is intended to cause the body to quickly enter a state of ketosis. Carbohydrate intake is limited to 20 net grams per day (grams of carbohydrates minus grams of fiber, sugar alcohols, or glycerin), 12 to 15 net grams of which must come in the form of salad greens and other vegetables. The allowed foods include a liberal amount of all meats, fish, shellfish, fowl, and eggs; up to 4 ounces (113 g) of soft or semi-soft cheese; salad vegetables; other low carb vegetables; and butter and vegetable oils. Alcoholic beverages are not allowed during this phase. Caffeine is allowed in moderation so long as it does not cause cravings or low blood sugar. If a caffeine addiction is evident, it is best to not allow it until later phases of the diet. A daily multivitamin with minerals is also recommended.
The Induction Phase is usually when many see the most significant weight loss — reports of losses of 5 to 10 pounds per week are not uncommon when Induction is combined with daily exercise.
Atkins suggests the use of Ketostix, small chemically reactive strips used by diabetics. These let the dieter monitor when they enter the ketosis, or fat burning, phase. Other indicators of ketosis include a metallic taste in the mouth, or bad breath.
Weight loss varies by person, especially based on the amount needed to lose, but on average most people achieve approximately 10% of the total weight loss within the Induction period.
The Ongoing Weight Loss (OWL) phase of Atkins consists of an increase in carbohydrate intake, but remaining at levels where weight loss occurs. The target daily carbohydrate intake increases each week by 2 net grams. A goal in OWL is to find the "Critical Carbohydrate Level for Losing" and to learn in a controlled manner how food groups in increasing glycemic levels and foods within that group affect your craving control. The OWL phase lasts until weight is within 10 pounds (4.5 kg) of the target weight. At first weeks you should add more of the induction acceptable vegetables to your daily products. For example, 6-8 stalks of asparagus, salad, one cup of cauliflower or one half of avocado. The next week you should follow the carbohydrate ladder Dr Atkins created for this phase and add fresh dairy. The ladder has 9 rings and should be added in order given. One can skip a rung if one does not intend to include that food group in one's permanent way of eating such as the alcohol rung.
The rungs are as follows:
- Induction acceptable vegetables
- Fresh dairy
- Other fruits
- Starchy vegetables
Carbohydrate intake is increased again this time by 10 net carbs a week from the ladder groupings, and the key goal in this phase is to find the "Critical Carbohydrate Level for Maintenance", this is the maximum number of carbohydrates you can eat each day without gaining weight. This may well be above the level of carbohydrates inducing ketosis on a testing stick. As a result, it is not necessary to maintain a positive ketosis test long term.
This phase is intended to carry on the habits acquired in the previous phases, and avoid the common end-of-diet mindset that can return people to their previous habits and previous weight. Whole, unprocessed food choices are emphasized, with the option to drop back to an earlier phase if you begin to gain weight.