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Increased Bone Marrow Fat in Anorexia Nervosa

Department of Radiology (M.A.B., M.T., B.J.T., R.H.G.) and Neuroendocrine Unit (P.K.F., K.K.M., M.M., A.K.), Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114; and Maine Medical Center Research Institute (C.J.R.), Scarborough, Maine 04074

Address all correspondence and requests for reprints to: Miriam A. Bredella, M.D., Massachusetts General Hospital, Yawkey 6E, 55 Fruit Street, Boston, Massachusetts 02114. E-mail: mbredella{at}partners.org.

Context: Although women with anorexia nervosa (AN) have severe depletion of body fat, a paradoxical increase in bone marrow fat has been described. Recent data suggest that marrow fat measured by 1H-magnetic resonance spectroscopy (MRS) in combination with bone mineral density (BMD) may be more valuable than either parameter alone in detecting bone weakness.

Objective: The objective of the study was to investigate the effect of AN on accumulation of marrow fat in spine and femur using 1H-MRS and the relationship between marrow fat, BMD, and body composition in subjects with AN and normal-weight controls.

Design: This was a cross-sectional study.

Setting: The study was conducted at a referral center.

Patients: Patients included 10 women with AN (29.8 ± 7.6 yr) and 10 normal-weight age-matched women (29.2 ± 5.2 yr).

Interventions: There were no interventions.

Main Outcomes Measure: Marrow fat content of the fourth lumbar vertebra and femur measured by 1H-MRS. BMD of spine and hip measured by dual-energy x-ray absorptiometry.

Results: Subjects with AN had higher marrow fat at the fourth lumbar vertebra and femur compared with controls (P = 0.004–0.01). There was an inverse correlation between marrow fat of L4 and femur and BMD of the spine and hip (r = –0.56 to –0.71, P = 0.01–0.0002) and body mass index and sc adipose tissue of the thigh (r = –0.49 to –0.71, P = 0.03–0.0007). There was an inverse correlation between femur marrow fat and sc and total abdominal adipose tissue (r = –0.53 to –0.67, P = 0.003–0.03).

Conclusion: Women with AN have greater lumbar and femoral marrow fat than controls, and marrow fat correlates inversely with BMD. This paradoxical increase in marrow fat at a time when sc and visceral fat are markedly reduced raises important questions about functional consequences of this process.