Fasting diets:

When we skip breakfast or dinner or stop eating for a prolonged period, the brain can not find the fuel needed to operate. As your body's priority is the health of brain, the muscle is sacrifice to provide fuel, when you lose your muscle the caloric expense decreases, each pound of muscle helps you burn 45 calories at day. This is just a body's defense mechanism designed to survive in times of famine. With fasting diets lose weight at high speed but most of what you lose is water and muscle, but your metabolism becomes slow and easily recovers the lose weight and more.

Diets without carbohydrate:

In this kind of diets it is allows eat all the proteins and fats that you want, but it prohibits the consumption of carbohydrates. As brain needs carbohydrates to work, it happen the same as in fast diets, you lose muscle and water. But as well as let you eat all meat, cheese, cold meats and animal fats desired increases the risk of suffer a cardiovascular disease and with the excess of protein damage the liver or kidneys. The person who follows this diet, feel dizzy, with headaches and the body begins to produce ketone bodies that seriously damage your health.