A prospective investigation of the relations among cognitive dietary restraint, subclinical ovulatory disturbances, physical activity, and bone mass in healthy young women.

BACKGROUND

Cognitive dietary restraint (CDR) may mediate subclinical ovulatory disturbances, which may result in loss of bone mineral density (BMD). CDR is associated with greater physical activity, which may modify the effect of CDR and ovulatory disturbances on bone mass.

OBJECTIVE

We aimed to investigate the relations among CDR, ovulatory disturbances, and physical activity and their effect on BMD in healthy premenopausal women over a 2-y period.

DESIGN

In this prospective cohort study, key explanatory factors, important covariates, and BMD were measured at baseline and at 12 and 24 mo; 225 women completed the baseline assessment, and 189 completed the study. CDR was measured with the Three-Factor Eating Questionnaire, and physical activity was measured with the Baecke scale. An average of 9.8 menstrual cycles in 2 y were monitored by using salivary progesterone measurements and urinary ovulation detection kits. Ovulatory disturbances included anovulatory cycles or short luteal phase lengths of <10 d. BMD at the lumbar spine, femoral neck, and total body was measured by using dual-energy X-ray absorptiometry. General linear mixed modeling was used to determine predictors of change in BMD over time.

RESULTS

CDR was not associated with ovulatory disturbances or changes in BMD. The average annual rate of change in lumbar spine BMD was decreased by 0.01 g/cm(2) in women who had experienced > or =3 monitored cycles with ovulatory disturbances (P = 0.02).

CONCLUSIONS

CDR did not predict bone loss, and there was no relation between CDR and ovulatory disturbances. Ovulatory disturbances had a negative effect on the rate of change at the lumbar spine. The cause of these disturbances is unknown.