Due to the EMR exposure, being on the go or what? I’d wager the folks who sit at a desk from 9 to 5 throughout the week aren’t any healthier and they probably hate their job too - go figure!
Myriad of reasons but my big ones are Sleep pattern disruption/time zone shifts, Radiation exposure, diet/fintess and exposure to unknown toxins (google Spirit pilot fumes).
Sleep pattern disruption and loss of sleep is the biggest one for me. On the domestic side I often had trips that fly a few legs to the west coast day one, redeye the following night (0100 departure on my body clock), land on the east coast at 0600. Day layover (try to sleep during day time on my body clock) then get up and fly a leg that night sometime after 8-9pm. Now that I'm international, it's depart the east coast around 8-10pm, fly 7-9 hours (with a 2 or 3 hour nap) and land in Europe around 0400 body clock, get in a bed around 0600 body time sleep for 2-4 hours then force yourself out of bed. Try to get a workout, wander around, get dinner then force yourself to stay up until about 1800 body time, sleep for a few hours, wake up at 0200 local time (everyone experiences this...), get back to sleep in an hour or so (if you're lucky), then wake up around mindnight to 0500 body time. Fly 7-9 hours home, land around 1500-1800 body time and then try to stay awake long enough to sleep as if it's normal body time. Get up and do it all over again. On a normal six day trip I estimate I lose a full night (if not more) of sleep...when I get home I'm wrecked for the next day. If I can keep it to just one leg over to Europe and back (3-day trip), I'm generally ok. Asia is killer and wrecks me for the day after the trip. I can't even imagine my buddies at the Cargo carriers that fly around the world, 10-day trips...or long haul corporate guys. Read
Why we Sleep by Dr Walker (or if you like Joe Rogan look up epsiode 1109), keeping a normal sleep pattern is vital for our health.
WRT radiation exposure. It's a relatively linear increase up to 350, then it increase exponentially. I often spend 6-11 hours between FL350 and FL410. LOTS of the Captains (mostly 60+ crowd) I fly with have had various forms of skin cancer cut out of them.
Obviously diet/exercise is a big one. Eating healthy is not unattainable, but just that much harder while on the road. Exercise is hit or miss given the long days and sleep pattern shifts. Given the choice of sleep or exercise, I'll sleep every time.
Don't get me wrong, I absolutely love my job and wouldn't want to do anything else. But it does take a toll on your body. I actually stopped bidding a line and bid reserve now to limit my exposure to that type of stuff (WB reserve pilots spend lots of time at home).