Stay off junk and fatty foods, eat more fruit and vegetables. I don't know if it works for you, but I read somewhere that you shouldn't eat 3 big meals a day, it's better if you eat smaller portions/little snacks in between the 3 main meals of the day and during the main meals, have it in smaller amounts. You should exercise to keep fit, too, but don't go for an all-out workout if you're just starting out; better to take it slow, like a 30 minute walk around the neighborhood every day for a week, then proceed to increase the amount you exercise from there.