There are a few health things that I think FF'ers need to be aware of. Some have been previously mentioned:
Flying:
1. Weight - Further discussed below in 2&3&4.
2. Over-Eating/poor eating. Airlines tend to feed you well when flying J or F. Even in Y, the food is often fatty and full of carbs. This helps pile on the weight.
3. Over-Drinking. Flying seems to be all about free drinks in J/F/lounges. Yeah people can resist alcohol, but a lot of people over indulge in lounges or onboard. Seems that Frequent Flying is also often about 'Frequent Drinking'.
4. Lack of exercise. Hard to exercise on a plane!
5. DVT and similar issues from non or limited movement during flight.
At destination:
1. Weight - Further discussed below in 2&3&4.
2. Over-Eating/poor eating. Too easy to either eat unhealthily due to lunches/dinners with clients/colleagues, or being too tired to order healthily when getting back to hotel, or unfamiliarity with local food and seeing Maccas as an acceptable option!
3. Over-Drinking. Again could be due to clients/colleagues, or just because of nothing else to do etc.
4. Lack of exercise. Too busy to use gym at hotel or go swimming etc. Don't know of local sports clubs or activities you would like. May not feel safe in general environment around hotel. Tend to catch cabs everywhere.
5. Depression/Loneliness/Stress - Could be related to the type of work you're doing and the timeframes you're under, could be to do with loneliness being away from home, or a perceived lack of things you think you could be doing.
6. TimeZones/lack of sleep - related to your body clock not adjusting quickly to your new time zone.
7. General health - eg vaccinations not up to date, poor choice of eating places could lead to different infections/sickness or disease.
Plenty of ways to get around these - it just takes time, motivation and a willingness to do something about it. For example, getting a studio/self contained apartment instead of a hotel and being able to cook your own meals rather than take-away, drinking in moderation, LowFat/LowCarb choices on planes and in restaurants, sleeping properly while away, allowing additional day to recover after arriving in a place, walking back to hotel from client's site, having alcohol free nights, or just going for a walk to see some of the sights.