@EtherRoom Heh. For Hollywood, I offer 12:1 odds.
No, doing sit-ups or other targeted exercises may or may not reduce fat on the stomach. What it will do though is strengthen those muscles, which may make it easier to hold your tummy in all day.
Often, when someone unintentionally loses their butt and boobs by exercising, it’s because they exercised too much. (Or are unlucky: there are also people who just dislike their own body appearance, and/or it does odd things like lose fat only from the places they don’t want it to.)
Remember that what you care about is your health, how you feel, and how you look. A common mistake is to use the scale’s opinion. One basic problem with the scale is that muscle weighs more than fat, and the scale only gives you your total weight (muscle + fat + skeleton + clothes + fluids + food + poop). If you choose a weight target and then exercise, you build muscle, which makes you denser, so you will need to lose more fat to make your weight the same, which can mean by the time you are 120 lbs again, you might have no boobs because you worked off too much to compensate for the weight of your new muscle. You’d do better to use a tape measure than a scale. It’s would be fine to weigh even more than you do, if your shape is what you want.
Of course there is the danger of looking at your own body and seeing problems where no one else does. I live far from Hollywood, but I still know many women who have awesome healthy bodies, on the thin side, but who complain and suffer and stress out when they see themselves in a mirror, buy clothes that are a size too small, deprive themselves of food, etc. And when they talk to each other, they often validate each others’ madness.