Bone density and amenorrhea in ballet dancers are related to a decreased resting metabolic rate and lower leptin levels
Kaufman, B.A.; Warren, M.P.; Dominguez, J.E.; Wang, J.; Heymsfield, S.B.; Pierson, R.N.
Journal of Clinical Endocrinology and Metabolism 87(6): 2777-2783
2002
ISSN/ISBN: 0021-972X PMID: 12050250 DOI: 10.1210/jcem.87.6.8565Document Number: 259440
Osteopenia, which is correlated with amenorrhoea and poor nutritional habits, has been well documented in elite ballet dancers. Oestrogen replacement therapy and recovery from amenorrhoea have not been associated with normalization of bone density. Thus, the osteopenia may be related to changes brought about by chronic dieting or other factors, such as a hypometabolic state induced by poor nutrition. The purpose of this study was to investigate the relationship of chronic dieting and resting metabolic rate (RMR) to amenorrhoea and bone density. RMR, bone density, eating disorder assessments, leptin levels, and complete menstrual and medical histories were determined in 21 elite ballet dancers and in 27 nondancers (age, 20-30 yr) in New York city, New York, USA. No significant correlations were found between high EAT26 scores, a measure of disordered eating, and RMR, bone densities, body weight, body fat, or fat-free mass. However, when RMR was adjusted for fat-free mass (FFM), a significant positive correlation was found between RMR/FFM and bone density in both the arms (P<0.001) and spine (P<0.05) in ballet dancers, but not in the normal controls. The dancers also demonstrated significantly higher EAT scores (22.9+or-10.3 vs. 4.1+or-2.4; P<0.001) and lower RMR/FFM ratios (30.0+or-2.2 vs. 32.05+or-2.8; P<0.01). The only variable to predict lower RMR/FFM in the entire sample was ever having had amenorrhoea this group had significantly higher EAT scores (18.0+or-13.5 vs. 10.3+or-10.2; P<0.05), lower leptin levels (4.03+or-0.625 vs. 7.10+or-4.052; P<0.05), and lower bone mineral density in the spine (0.984+or-0.11 vs. 1.10+or-0.13; P<0.05) and arm (0.773+or-0.99 vs. 0.818+or-0.01; P<0.05). We hypothesize that the correlation between low RMR and lower leptin levels and bone density may be more strongly related to nutritional habits in ballet dancers, causing significant depression of RMR, particularly for those with a history of amenorrhoea.