Nuts can be eaten during Phase 2 of the Atkins diet. During Phase 1, many foods are cut out of the diet to limit daily carbohydrates to 20 grams, notes the diet's official website.
The theory behind the Atkins diet is that once carbohydrates are cut out of the diet, the body begins to use fat stores for fuel. There are four phases of the Atkins diet. The first phase is called the Induction phase. No more than 20 grams of carbohydrates are allowed. Poultry, fish, eggs, red meat, butter and vegetable oils are allowed during Induction. Each additional phase allows more foods such as nuts and fruits to be added back to the diet, according to the Atkins Nutritionals website.