First thing the BMI only a guide
Most rugby players would fail it as it does not take into account people who are built tough ie mesomorphs ie Polynesians
Second no one has mentioned friends and family , its important to have good friends even if you live less and have lots of beer and fun with your mates its better than living along time drinking fruit juice by yourself.
Third exercise should just be a part of your everyday life and maybe a bit of cardio to push the hart rate above 75% of theoretical maximum for at least 20 minutes 3 times a week and some weights for resistance training.
Fourth genetics is a big factor one side of my family lived into their 80s and were in the beer industry , i have the records back to 1680 the other side died in their 50s.
Fifth life style obviously smoking is naughty ( but why do Japanese who smoke live a long time) also should monitor Blood pressure , Insulin , skin cancer , prostate, with check ups.