Physical measures of recovery from anorexia nervosa during hospitalised re-feeding.

OBJECTIVE: To examine the relationship between weight gain, changes in body composition and physiological characteristics of fitness during the recovery from anorexia nervosa.

DESIGN: Longitudinal over eight weeks of intensive inpatient re-feeding (Wk 0-8).

SETTING: The London Hospital Medical College.

SUBJECTS: Ten female patients who agreed to participate. Seven completed the protocol.

INTERVENTIONS: Dual-energy X-ray absorptiometry (dexa) and skinfold thickness measures at Wk 0 and 8. Weekly measures of peak expiratory flow rate and cycle ergometry (several variables relating to aerobic work recorded at rest and during cycling at low loads (0-60 W)). Blood samples for lactate and potassium measures, taken during cycling at Wk 0, 4 and 8 only.

RESULTS: (1) Body composition: Mean weight gain over eight weeks was 9.6 kg, dexa and skinfold measures showing fat gain to contribute 62% and 54%, respectively. Both methods showed significant changes in percentage body fat with refeeding (P < 0.01 and P < 0.001, respectively), however there were significant differences in results between methods before (P < 0.01) but not after (P = 0.2) refeeding. (2) Physiological function: Between weeks 0 and 8, mean peak expiratory flow rate rose to 85% of predicted values, cycle ergometry performance improved in six subjects (three never reached 60 W load), mean respiratory exchange ratio (RER) during cycling fell at 0 W and 20 W loads (both P < 0.05), and oxygen pulse increased at rest and 0 W load cycling (both P < 0.05), Wk 8 values being well below normal. Oxygen uptake at rest and all loads increased in line with body weight gain only. No significant changes were seen in heart rate or blood lactate and potassium levels.

CONCLUSIONS: (1) Lean body and fat mass increased significantly during eight weeks of refeeding. The methodological difference in initial body fat measurements requires further investigation. (2) The women had severely impaired physiological function. Variables studied were only slowly improving with refeeding, and work capacity was still well below normal.