"The revolution in nutrition" (that was the name of the first book of the famous American doctor) was that to lose weight you need to eat a lot of protein and fat (ie meat, eggs, cheese in unlimited quantities), carbohydrates are almost unnecessary. This means that not only will have to avoid sweets, but also fruits, vegetables (with rare exceptions), cereals and more. Because the shortage of carbohydrates (the main source of energy for humans) in fat consumption is out of stock.
Pros. "In Atkins' really lose weight quickly and inevitably...
Cons.... But at the cost of health, not only physical, but also mental. The brain needs carbohydrates, so the protein diet deteriorates attention, memory, and mood. Suffers from an excess of fat liver from excess protein - the kidneys. It is necessary to get off the diet - weight gain is inevitable. A long time (over a week) to sit on it, you should not.
By the way, Dr. Atkins died at the age of 73. The man who all his life teaching people to lose weight, with growth of 180 centimeters, weighs... 117 lbs. That is, not only was overweight, but obese.