Lengthy fasting can be dangerous due to the risk of malnutrition and should be carried out only under medical supervision. During prolonged fasting or very low calorie diets the reduction of blood glucose, the preferred energy source of the brain , causes the body to deplete its glycogen stores. Once glycogen is depleted the body begins to fuel the brain using ketones, while also metabolizing body protein (including but not limited to skeletal muscle) to be used to synthesize sugars for use as energy by the rest of the body. Most experts believe that a prolonged fast can lead to muscle wasting, although some dispute this. The use of short-term fasting, or various forms of intermittent fasting have been used as a form of dieting to circumvent this issue.
Sudden muscle weakness. This is because the muscle tissues are deprived of adequate amounts of protein during the first few days of the diet plan. This condition can be regulated once the system gets used to the nutrients provided by the regimen.
Incessant thirst and dehydration. Persons following the GM diet also feel incessantly thirsty and even suffer from dehydration as their fluids are used by the body to foster metabolic processes. Followers are therefore advised to take more water to prevent the onset of dehydration and experience a more rejuvenated feeling.
Headaches and malaise. Persons who are in their first days of the GM diet may experience headaches and malaise, as they are still on the process of getting used to the diet effects. These tend to be psychosomatic, as followers are subject to cravings which have to withstand in order to achieve their diet goals.