Also, while the exact numbers are a bit contentious, having a BMI over 40 undoubtedly decreases your life expectancy.
For example, one study predicts that an adult male non-smoker with a normal BMI throughout life has a life expectancy of 81 years.
If that same person has a BMI over 40, their life expectancy is only 71 years.
If that same person smokes and has a BMI over 40, their life expectancy is only 60 years.
Makes you think twice about the age 65 rule when obese smokers don't get any extra scrutiny.