Based on the book "Dr. Atkins' Diet Revolution," published in 1972 by Dr. Robert Atkins, the Atkins Diet restricts intake of certain foods to trigger weight loss. By Dr. Atkins' own admission, the diet is a drastic measure for obese people. The fact that the early part of the diet is limited in vegetable intake and focused on meats and cheese has made it the target of critics, but the positive results of the diet seem to speak for themselves. Nuts are one of the healthy foods that are not allowed early in the Atkins Diet, but which are gradually phased back in as the diet progresses.
The term "nut" is a bit ambiguous because in common usage it includes some specimens, like pistachios, that are not nuts in the biological sense. Technically, a nut is a type of fruit with a single seed. At maturity, the ovary wall hardens, becoming a shell and the seed inside remains soft and edible. Many seeds, like almonds, cashews, macadamia nuts and brazil nuts, are nuts only in a culinary sense. Peanuts are actually legumes. Nuts are nutritionally significant because they contain essential fatty acids. They also contain significant levels of protein and carbohydrates.
During the induction phase of the Atkins Diet, the most strict period, no nuts are permitted. The purpose of the induction phase is to get the body accustomed to burning fat by starving it of other energy sources. Eggs, meat and cheese are staples of the induction phase. Small amounts of vegetables can be consumed because most of their carbohydrate content is indigestible fiber. Nuts are too rich in digestible carbohydrates to be recommended during the induction phase.
The ongoing weight loss (OWL) phase of the diet allows additional carbohydrates according to a rule called the Power of Five. Certain foods are allowed in portions that have five or less net carbs, calculated by subtracting dietary fiber from total carbohydrates. Servings of nuts with five net carbs or less are 30 almonds, 10 Brazil nuts, nine cashews, 12 macadamia nuts, 10 pecan halves, 50 pistachios or 14 walnuts.
As you reach your target weight, you move from the OWL phase into pre-maintenance. The scope of acceptable foods increases, but portions are carefully controlled to limit total carbohydrate intake. Consumption is now governed by the Power of 10. Add 10 grams of carbohydrate to your daily intake, and add another 10 each week until your weight loss stops. The plan calls for the same portions and types of nuts allowed in phase 2 with the addition of certain legumes, fruits and vegetables to provide these additional grams of carbohydrates.
Once you reach your target weight, you transition to the maintenance phase of the Atkins diet. No food is strictly off limits in this phase. The goal, however, is to remain within the the range of carbs you were consuming at the end of the pre-maintenance phase. This is what Atkins calls the Atkins Carb Equilibrium, or ACE. A carb counter is provided to ensure that total carb intake, including from nuts, stays at the equilibrium level.