How to not gain a pound after eating this?

You already had about 800-900 calories with the 4 poptarts you ate and the high calorie meal you ate probably bumped up your calories to around 1,500 or so. The oat meal was healthy which is about 100 calories. That's about the amout of calories you're supposed to have in one day. Don't go without eating the rest on the day though. Eat a healthy dinner with a lean meat and some veggies and drink lots of water. Tomorrows a new day:D