Current clinical guidelines and public health statements generically prescribe body mass index (BMI; kg m(-2)) categories regardless of the individual's situation (age, risk for diseases, and so on). However, regarding BMI and mortality rate, two well-established observations are (1) there is a U-shaped (that is, concave) association-people with intermediate BMIs tend to outlive people with higher or lower BMIs; and (2) the nadirs of these curves tend to increase monotonically with age