This is from www.atkins.com-I am not promoting Atkins, but it is a good explanation of how it all works! My high protein diet, based on weight loss surgery principles, follows the same theories.HOW AND WHY ATKINS WORKS:Atkins turns your body into a fat-burning machine. Metabolism is the process that converts food into either energy or your body’s building blocks. Eating the right foods can improve your body’s metabolism, particularly how it handles fat. When you eat fewer carb foods—relying mostly on vegetables rich in fiber—your body switches to burning fat (including your own body fat) instead of carbs as its primary fuel source.

Get an exit pass off the blood sugar roller coaster. When you digest carb foods, they convert to glucose (sugar), which your bloodstream transports throughout your body. A rise in blood glucose level triggers the release of the hormone insulin, which moderates your glucose level. So carb intake is largely responsible for blood sugar fluctuations. Food need not taste sweet—think mashed potatoes and white bread—to convert rapidly to glucose.

Because your body can store no more than half a day’s energy supply of glucose—unlike our ability to store almost limitless amounts of fat—it makes sense that we burn as much carbohydrate as we can as soon as it’s digested and absorbed. After each carb-heavy meal or snack, your body stops burning off fat as your insulin level escalates to deal with the rising tide of blood sugar. Fat calories are always pushed to the back of the line—where more than likely they’re stored. That’s why insulin is called the “fat hormone.” As long as you keep making glucose into fat, you’re doomed to being heavy.

Fortunately, it doesn’t have to be that way. That’s why cutting your carb intake and eating mostly whole food carbohydrates is the core premise of the Atkins Diet.

By changing the balance of carbs, fats and protein in your diet, you boost your energy level and keep it on an even keel. When you eat foods composed primarily of protein, fat and fiber, your body produces far less insulin. And when the carbs you do eat are in the form of high-fiber whole foods, which convert to glucose relatively slowly, your blood sugar level holds steady, along with your energy level. You don’t crave a fast-fix energy booster in the form of sugary, starchy food. And you’re less hungry at meals.

This perfectly normal process of burning primarily fat for energy has a welcome side effect: weight loss. There’s nothing strange or risky about a primarily fat metabolism. In fact, fat is your body’s back-up energy source. The ability to carry a “fanny pack” of energy in the form of fat actually helped our distant ancestors survive in times of famine and when hunters returned home empty handed.

Just to be clear, eating fats doesn’t make you fat as long as you give your body permission to burn them. Place the blame where it belongs: overeating and overreacting to carbs. And herein lies the not-so-secret secret of the Atkins Diet and the key to weight loss—and later weight maintenance—without cravings or undue hunger.