Most Helpful Guy
You mention a flat stomach and better legs and arms, and you want to keep your derriere or chest. First of all, fat deposits distribute themselves depending on one's genetic endowment and change with age and endocrine, or hormonal, function. Second, you'd have to run for an hour to burn just 300 calories, so exercise helps only a bit in weight loss, as the experts say, but if you indeed do such exercise daily it can aid marginally in keeping caloric intake below your daily target (say 1600 to 1800 calories/day for weight loss).
Targeting large muscle groups of the legs and back will burn more calories because you use heavier weight and more exertion on exercising those groups (see calorie definition). If you have a club, do stair climbing, stationary biking, rowing, et cetera because those require much effort as well as aerobic-cardiovascular exertion while keeping to a minimum harmful impact on your joints. For definition, though, you want high reps, and for your arms the weight is not so important if you do high reps (if you don't want bulk).
Of most importance, though, is diet. Avoid meat, especially red meat. By going vegan you will lose at least 15 pounds permanently the first year. This means brown rice, tofu, beans, and lots of nuts for protein. Avoid breakfast cold cereals, dairy, cheese, fruit juice, bananas, pasta, corn, and anything with HFCS. Continue raw fruit and veggies for vitamin-mineral needs. Red pepper and garlic mixed in food might help control appetite, as would coffee. Avoid sugar in any form because it makes you hungrier later.
Exercise and diet as I outline will keep you from getting too hungry during the day, but you will develop will power against overeating and come to enjoy a nearly empty stomach because it makes you feel better.
If you get hungry at the wrong time, go for a walk instead or run in place one minute. You will do all this because you want to.