Nine patients experienced profuse hair loss two of five months after starting a vigourous weight reduction program resulting in weight loss of 11.7 to 24.75 kg. Telogen counts of 25% to 50% were observed. Regrowth of hair occurred within several months. Three patients had experienced hair loss closely following a successful weight reduction program on several occasions. Rigorous caloric restriction with subsequent inadequate energy supply of the hair matrix is thought to be the cause for the precipitation of the telogen effluvium of the crash dieter.