Dietary restraint, exercise, and bone density in young women: are they related?

Purpose: Women with high scores for dietary restraint have been found to ha ve higher 24-h urinary cortisol excretion and a higher prevalence of subcli nical ovulatory disturbances, both of which may be risk factors for bone lo ss. The purpose of this study was to explore relationships between dietary restraint and bone health in regularly menstruating young women, Methods: 6 2 women (age: 21.7 +/- 2.5 yr) had body composition and total body and lumb ar spine bone mineral density (BMD) and content (BMC) assessed using dual-e nergy x-ray absorptiometry. Dietary restraint was assessed using the restra int subscale from the Three-Factor Eating Questionnaire: 29 women had low r estraint (LR: restraint score 0-5), 33 had high restraint (HR restraint sco re 13-21). Exercise (h.wk(-1)) was assessed by questionnaire on two occasio ns. Results: LIZ and HR women were similar in age and body composition (fat mass = 15.0 +/- 4.7 kg, lean mass = 40.9 +/- 4.9 kg), but HR women exercis ed more (3.4 +/- 1.7 vs 2.2 +/- 1.8 h.wk(-1), P < 0,05). Exercise was corre lated with BMD and BMC, and when it was included as a covariate, total body BMC was significantly lower in HR than LIZ women. In multiple regression a nalysis, weekly hours of exercise and restraint score were significant pred ictors of total body BMD and BMC. Conclusion: The observations of this cros s-sectional study suggest that high levels of cognitive dietary restraint, or associated factors such as higher cortisol. may attenuate the positive e ffects of exercise on bone in young women.