The level of daily physical activity in 11 non-hospitalized women with anorexia (age: 21-48 yr, body mass index (BMI): 12.5-18.3 kg·m-2), compared with 13 normal-weight women (age: 20-35 yr, BMI 19.2-26.7 kg·m-2), was studied in relation to BMI. Daily physical activity over a 7-d period was determined from movement registration and by combining measurements of average daily metabolic rate (using the doubly labeled water method) and sleeping metabolic rate (measured in a respiration chamber). Group averages of daily physical activity were similar for subjects with anorexia and control subjects. However, women with anorexia had either a low or a high level of daily physical activity, whereas most control subjects had a moderate level of daily physical activity. In the women with anorexia, daily physical activity was significantly related to BMI (r = 0.84). Subjects with a BMI ≥ 17 kg·m-2 were equally or more active compared with control subjects, while subjects with a BMI < 17 kg·m-2 were equally or less active compared with control subjects. The increased physical activity at BMI ≥ 17 kg·m-2 is considered to be facilitated by an improving physical capacity combined with the advantages of a low body mass during weight-bearing activities. At lower BMI, undereating and declining physical capacity may have caused the observed decrease in daily physical activity.
Division of Computational and Experimental Mechanics, Eindhoven University of Technology, 5600 MB Eindhoven; and Department of Human Biology, University of Limburg, 6200 MD Maastricht, THE NETHERLANDS
Submitted for publication June 1995.
Accepted for publication February 1996.
The authors would like to thank Brigitte Jongen for her assistance during the experiments and Loek Wouters for assistance with the isotope analysis.
Address for correspondence: Dr. Carlijn V. C. Bouten, Faculty of Mechanical Engineering, Department of Fundamentals, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, the Netherlands.