Packing your own food when possible vs. buying the high fat crap at the terminal is a good first step for health. After I was displaced from the left seat I started to pack food to cover one or two meals per day. I would store this food in the fridge provided by the company. My intent in doing this was to save money but I got a nice unexpected reward. In about 8 months I lost 15-20 pounds. Of course the kind of flying that you do will determine if this is a feasible option for you.