Bone stiffness index score determined from quantitative ultrasound measurement provides an indication of bone quality in young women and may be related to dietary habits and levels of physical activity. PURPOSE: The purpose of the study was to examine the relationship between quantitative ultrasound (QUS) bone stiffness index (SI) score, body composition, dietary restraint, and metabolic equivalents (MET) as indicated by hours per week of physical activity. METHODS: Twenty-four healthy Caucasian females aged 19 to 22 were recruited to participate from campus health fairs and undergraduate classes. Subjects completed a personal health history form, the Dutch Eating Behavior Questionnaire Restraint Scale (DEBQ-R), and the International Physical Activity Questionnaire (IPAQ). Participants also were measured for height and weight and participated in three QUS measurements of their right calcaneus. RESULTS: No subj ect reported current use of any medication known to influence bone mineralization, and 21 subjects (87.5%) indicated that they did not smoke. Mean descriptive values and ranges were as follows: QUS SI = 103.4 ± 18.3, range 76.0-141.0; weight = 60.0 ±9.8 kg, range 42.5-86.2 kg; height = 163.5 ± 8.5 cm, range 144.5-176.8 cm; BMI = 22.5 ± 3.7, range 17.5-32.4; DEBQ-R score = 26.1 ± 5.5, range 15-40; and IPAQ score = 90.6 ± 76.6 METhrs/week, range = 5.4-310.9 MET hrs/week. Pearson r correlation coefficients indicated moderate relationships between SI and DEBQ-R score (r = 0.47, p =.02) and IPAQ score (r = 0.52, p = 0.01). In this group of females no association was observed between SI and BMI (r = 0.27, p = 0.20) or between DEBQ-R and IPAQ scores (r = 0.03, p = 0.88). CONCLUSION: Bone quality estimated from QUS SI score appears to be positively associated with both restrained eating and weekly amounts of physical activity. While the relationship of bone health with physical activity behaviors is understandable, the positive association of restricted eating with bone quality is puzzling and warrants further investigation.