A high-protein, low-carb diet, such as the Atkins diet, is meant to trigger weight loss and help keep the body's metabolism high. There have been successes with these diets, but most people have found that once they lose the weight, it comes back slowly and cannot be removed by the same methods. Also, there is a significant danger of muscle loss and constipation.
Most diet books using this method suggest remaining on the extreme-low-carb diet for as long as it takes to lose your weight goal, and then alter the diet over time to maintain your weight. The problem is that by training your body to burn fat instead of glucose, you risk a metabolic state called Ketosis, which can cause organ failure in the body. Other risks include kidney stones, high cholesterol, and osteoporosis. Most nutritionists suggest eating carbs in moderation, but not eliminating them or cutting back below 100 grams per day.
In recent years, new and safer methods of low-card dieting have appeared, such as carb-backloading, in which carbs are consumed in the evening after an exercise session; the theory is that after exercise the body is trying to burn glucose and build muscle, so the body burns the carbs directly. These methods are still being reviewed.