Resting Metabolic Rate Before and After Weight Gain in Anorexia Nervosa

Do patients with anorexia nervosa have an abnormally low “set point” that is actually the engine that drives their weight loss? This is not the case, according to Laurel Mayer, M.D., and her colleagues. Instead, after normalization of body weight, the ratio of resting energy expenditure to free fat mass (REE/FFM) is significantly higher for patients with anorexia nervosa than for controls at usual body weight. The researchers discovered this pattern in a study of 11 patients with anorexia nervosa and 9 never-obese women (controls). The authors, who presented their study at last fall’s Eating Disorders Research Society Meeting in Boston, have two theories about the elevated REE/FFM among weight-restored AN patients. First, the elevated REE/FFM ratio may provide a potential physiologic explanation for the clinical difficulty patients experience in maintaining normal weight, or second, AN patients may develop a disturbance in REE during the course of the illness, which then helps perpetuate the disorder. Studies of long-term weight-restored AN women and women at risk for developing AN in the first place are needed to assess whether elevated REE/FFM ratios are present in these populations. Such alterations might support the view that metabolic differences exist in enduring “traits” rather than simply in “states” that result from starvation and inadequate recovery.