Data are men and women in the Health and Retirement Study (HRS) observed in waves 8 (2006) and 9 (2008)
r8agey_m = age at middle of wave 8 interview
r8weight = self-reported weight (kg) in wave 8
r9weight = self-reported weight (kg) in wave 9
r8smoken = 0/1 smokes in wave 8
r9smoken = 0/1 smokes in wave 9