The Basics
The core concept of The Atkins Diet is Dr. Atkins' theory that over-consumption of and hypersensitivity to carbohydrates is the root of our problem with being overweight. The principle he bases his plan on says that it is the way your body processes the carbohydrates you eat -- not how much fat you eat -- that causes you to gain weight.
Atkins says that many overweight people may be "insulin resistant," that is, the cells that convert carbohydrates into glucose (which becomes energy) do not work correctly. While most diet experts say that not everyone who has a weight problem is insulin resistant, Atkins says it is more likely than not.
That's where Dr. Atkins' plan comes in: What is the remedy to insulin resistance or over-consumption of carbohydrates? Begin restricting yourself, particularly from eating the "bad" ones like those found in processed, pre-packaged and junk foods (cookies, sodas, etc.) and prepare to follow this high-protein eating plan.
How Does it Work?
By reducing your carbohydrate intake to less than 40 grams a day, you will enter a bodily process called ketosis. Ketosis is a state in which your body burns fat as fuel. Atkins also says that ketosis will affect insulin production which will prevent more fat from being formed. Atkins' plan suggests that once you enter ketosis and your body begins efficiently using the fat as fuel, your cravings for carbs will subside and you won't miss the foods you are doing without.
The Phases and the Food
The Atkins Diet consists of the following four stages: induction, ongoing weight loss, pre-maintenance and maintenance. Induction is the first 14 days of the plan, during which Atkins says you can lose up to 15 pounds. This rapid weight loss is due to limiting your carbs to 20 grams a day. The only carbs you can have are low-carb vegetables like lettuce, broccoli and tomatoes. You are limited to three cups per day. Forget about yogurt, fruit and starchy vegetables like potatoes. If you consume alcohol or caffeine, you're going to have to say "sayonara" to those beverages as well.
During the next stage -- ongoing weight loss -- you can increase your carb intake by five grams. You will eventually hit a plateau and have to slack off your carb intake once again. During pre-maintenance, weight loss will happen a little more slowly and you will be able to "test" certain foods to see if you can safely add them to your diet without weight gain resulting. Once you reach your goal weight, you enter maintenance and may introduce some more carbs back into your diet but not the "bad" ones, as they will result in the weight returning. You will be asked to choose healthy carbs instead, whole wheat bread, for example.
The Atkins plan was referred to as "the most severe [diet] of the high-protein/low-carb school" in a March 2000 U.S. News article (Kulman). The article goes on to give examples of the diet's meals, which include bacons and eggs and cheeseburgers. The bottom line is you're really going to have to enjoy eating meat to like this plan!

