To the Editor.— The recent letters of Drs Goette and Odom ( Arch Dermatol 111:930, 1975; JAMA 235:476, 1975) regarding hair loss during rapid weight loss deserve comment. Over the past four years, we have been investigating the metabolism of modified fasting. We 1 and others 2 have observed the increased telogen hair counts but only in patients in whom weight loss was associated with loss of body cell mass (eg, significant negative nitrogen balance). With an increase in protein intake during fasting to preserve nitrogen balance, hair loss has been almost completely eliminated. We would conclude that when mobilized body protein plus dietary protein are insufficient to meet requirements, the low priority of hair growth for available protein accounts for the telogen effluvium and not the rapidity of weight loss per se. These data are derived from over 200 subjects in whom weight loss approached one fourth of a kilogram