Dangers of Rapid Changes in Caloric Intake (Fad Dieting)

Rapid changes in caloric intake, under nutrition, the administration of T3 or selenium deficiency lead to decreased activity of the 5'-Monodeiodinase enzyme. When this happens, the production of thyroid hormone T3 decreases and a decline occurs in the degradation of reverse T3. This decreases lipid metabolism, so called fat burning, and increases muscle wasting. Attempts to counter the situation by the administration of T3 make the situation worse. This is the body’s method of preventing starvation during a famine by rapidly shedding muscle while retaining body fat. Repeated episodes can lead to a dangerous weakening of the heart.