e12514 Background: Post-diagnosis weight gain is a risk factor for cancer recurrence and many individuals diagnosed with breast and ovarian cancer gain weight during and after treatment. In the present study, we have measured the anthropometrics of cancer survivors with BRCA mutations and have studied the association between anthropometrics and post-diagnosis weight gain. Methods: The study population included 37 breast and ovarian cancer survivors with BRCA mutations, 45 BRCA previvors, and 26 controls. Anthropometric measurements included body mass index (BMI; kg weight/ m2 height) and body composition (% fat and lean tissue, assessed by using 4-lead bioelectric impedance). Post-diagnosis weight gain was determined via questionnaire. Potential effectors of anthropometrics included: diet (3-day food records), physical activity (General Practice Physical Activity Questionnaire), physical health (co-morbidities, Rand-36 Physical Health Quality of Life (QoL)), and psychological status (Beck Anxiety Inventory, Rand-36 Emotional Health QoL). Results: We found no significant differences in BMI between the survivors, previvors or controls (26+2 (SEM), 25+1, 25+1, respectively). However, the % lean body mass of the cancer survivors was significantly lower and their % body fat significantly higher than the previvors or controls (p=0.0005). Measures of body composition (% fat and lean mass) were independent predictors of post-diagnosis weight gain (r=0.86, p<0.001). No significant association was found between body composition measures and psychological status, energy intake or food composition. However, the adverse body composition measures of the survivors were associated significantly with physical inactivity (p<0.01), number of co-morbidities (p<0.0001), and physical health QoL (p<0.01). Conclusions: BRCA cancer survivors have adverse changes in body composition that increase their risk for weight gain and disease relapse. Based upon these findings, it is important for the survivorship care plan to include: 1) education regarding post-diagnosis weight gain, 2) a physical activity regimen, 3) health management, and 4) interval assessment of anthropometrics, including body composition, during and after treatment.