Bone mineral density and body mass composition measurements in premenopausal anorexic patients: the impact of lean body mass.

Introduction: Evaluating bone density and body composition by dual-energy x-ray absorptiometry (DXA) and analyzing their relationships among young anorexic women in comparison with normal-lean matched controls.

Materials and methods: In this observational cohort study, 98 normal-underweight young females were enrolled (aged more than 16 and less than 24 years). The study group included 68 anorexic patients and 30 healthy age-matched controls. The patients underwent a DXA examination to evaluate bone mineral density and body composition. Several indexes of body composition were used: the FMI (Fat Mass Index), the TLMI (Total Lean Mass Index) and the SMI (Skeletal Muscle mass Index) the last one as a marker of sarcopenia.

Results: According to the ISCD (International Society for Clinical Densitometry) criteria, a significantly higher percentage of anorexic patients were found to be below the expected range for age as compared to controls (P < 0.01). According to WHO criteria, 20% of the anorexic patients presented an osteoporotic T-score index at the lumbar level and 18% presented an osteoporotic T-score at the femoral level. As regards the lean body characteristics, the SMI and TLMI were significantly lower in the anorexic population (P < 0.01 and P < 0.001, respectively) and 24% of the anorexic patients presented SMI values that are indicative of pre-sarcopenia. In addition, only the SMI significantly correlated with both the lumbar and the femoral BMD values.

Conclusion: Anorexic patients have a very high risk of osteoporosis and fractures. Bone density is influenced by fat body mass and also significantly by lean body mass. Special consideration should be given to the sarcopenic condition since it is a worsening factor of bone health.