Being Obese, weight-history period was taken prior to baseline (start of the 12-year follow-up), which was considered an adequate period of time to obtain minimally biased estimates of BMI. Longitudinal data were drawn from the US Nurses' Health Study 1 and 2, as well as the Health Professionals Follow-Up Study (HPFS), and the potential associations between different categories of BMI with all-cause mortality and cause-specific mortality were generated. There are genetic, interactive and hormonalimpacts on body mass, Obesity occurs when you take in more calories than you burn through exercise and normal daily activities. Your body stores these excess calories as fat.