Restrictive Anorexia Nervosa (ANR) is a clinical mental disorder defined as abnormal eating behavior and is often associated with physical hyperactivity. There is no consistent cut-off use to define what is considered excessive physical activity in term of duration, frequency and intensity in contrast with healthy physical activity (1). On the other hand, ANR is marked by bone loss and with low Body Mineral Density (BMD)(2). Few data are available in daily patterns of Physical Activity and in the relationship between time spent in moderate to vigorous PA and Bone Mineral Density (BMD) PURPOSE: To determine the association between time spent in moderate to vigorous physical activity (MVPA) and BMD in females with anorexia nervosa. METHODS: 17 females with anorexia nervosa (22+2 yrs) were included in the study. Body composition was assess by DXA measurements (Hologic QDR-4500W, Waltham, MA). 24h Physical activity levels and sleep time were monitored by using actigraphy (ActiSleep and ActiGraph GT3X, Pensacola, US). RESULTS: Females with diurnal higher VPA levels demonstrated an increased in integral Femoral Neck Bone Mineral Density (FNBMD) (0.678 g/cm2 vs. 0.623 g/cm2) compared to those with lower diurnal VPA levels (p<0.05). Time spent in light physical activity (LPA) is associated with a significantly lower total hip BMD (g/ cm2)(0.788 ± 0.11 vs 0.873 ± 0.15 ; p< 0.001). CONCLUSION: This investigation shows that ANR females accumulating more total Vigorous Physical Activity presented increased BMDs when compared to their less active peers. These data highlight the importance of VPA in females with AN to counteract their low bone mass and to improve their bone health. High time spent in LPA may be considered to be deleterious for BMD.