You can lose weight quickly on Atkins, but many people find as soon as they go back to normal eating, they regain the weight and sometimes more.
Atkins is based on cutting down on Carbohydrates drastically, so in the first few weeks you cannot eat many Carbs. So no bread, potatoes, pasta, rice, milk, most vegetables and fruit, confectionary etc.
You can, however, eat as much Protein and fat as you like. So any kind of meat, eggs, cream, oils. I think the reason you lose weight rapidly, is purely because you are halving your daily calorific intake. Carbs tend to be quite high in calories.
You'd be better off just eating a healthy, balance diet and exercising regularly. You also have to consider if consuming so much protein and fat will affect your general health.