Mayo:Low-carb diets

Low-carb diets limit carbohydrates — for example, bread, grains, rice, starchy vegetables and fruit — and emphasize sources of protein and fat. Many types of low-carb diets exist, each with varying restrictions on the types and amounts of carbohydrates. Examples of low-carb diets include Atkins diet, Zone diet and Protein Power.

Purpose

Low-carb diets are generally used to lose weight. You might choose this type of diet because you enjoy the types and amounts of food featured in the diet. Or, you may believe that a low-carb diet will help you lose weight quickly and easily.

Diet details

Premise
Carbohydrates raise blood sugar levels, which then kicks in insulin. The theory behind low-carb diets is that insulin drives blood sugar into the cells and prevents fat breakdown in the body. This means you won't burn excess fat and lose weight.
Proponents of low-carb diets take this one step further. They say that if carbohydrates raise blood sugar and insulin levels and cause weight gain, a decrease in carbs will result in lower blood sugar and insulin levels, leading to weight loss. And because you're not eating the carbs, your body breaks down fat to provide needed energy. Some people do lose weight on low-carb diets, but the weight loss probably isn't related to blood sugar and insulin levels.
Typical menu
In general, low-carb diets focus on meat, poultry, fish, dairy products, eggs and some nonstarchy vegetables. The diet excludes or limits most grains, beans, fruits, breads, sweets, pastas and starchy vegetables. Some low-carb diet plans allow fruits, vegetables and whole-grains.