Going back to the question of losing weight by exercise (because Badgerdaddy is sure to pull me up over it) yes, it's possible if you do enough. I know a bloke who cycled across America, coast to coast from Virginia to California, in 3 months and, after the first week, realised he had to double the amount of food he was eating to keep pace with the work he did. But he had been training and preparing for this trip and was used to going to the gym and cycling about 30 miles a day, and he hadn't lost weight on that - he wasn't trying to, he was lean and fit already. So if you're going down the hard exercise route, do that for its own sake. I'm sure you'll lose weight, but it'll take longer if you haven't changed the way you eat.
Many of us have dieted before and either lost weight and put it on again or not lost much at all. So I think you need to work out what you are eating wrong and why. We often say that we don't really eat that much and we've got friends who eat a lot more and don't put on weight, but that's got nothing to do with it. If we're overweight it's because we eat and drink more and move around less than we need to. It doesn't help to compare ourselves with others, unless it's to see what they are doing right, maybe unconsciously, and therefore why they are thinner than we are.
Once you know what you're doing wrong, you must address the reason. Then, you need to work out how to get around that. I find that I must always have something to snack on, but if it is pretty uninteresting and low fat then I won't be tempted to pig out on it, and it doesn't really matter if I do. If you have a strong craving for a food, then it's best to go without. Sweet and fatty foods cause cravings. If you have a really low fat diet for a week and then eat some chips, the fat will coat the roof of your mouth and you'll wonder why you never noticed it before.
But there are various reasons we overeat and it's not enough to simply decide not to do it again. For example, if you've been brought up to clear your plate, it can be really hard not to. If you're sociable, then as you chat, you eat and you don't notice how much you are eating. If you are unhappy or lonely, food is a comfort. it's a great comfort. Don't underestimate that. If we don't care much about food then we'll just shovel it in, but if we're a gourmet then we cook elaborately. We may not be aware of hidden fat, such as in dressed salads or sauces. Then there's those of us who eat carefully all week, go out on a Friday night and eat several packs of crisps and nuts with our gallon of beer, finishing with cheese-laden pizza on the way home.
So, identify what makes you overeat and what you can do about it. Just as importantly, work out what you can't help or what triggers you might be able to avoid. Be honest with yourself, but don't do it with an attitude of self-hate. That is part of the problem. We don't like our bodies when we're fat. Eating sensibly is not a punishment. It's a choice. And, sorry to point it out, but it's for life. If you diet, lose weight and then stop dieting and taking exercise, odds are that you'll regain all you lost and more, in a dismayingly short time. No, it's not fair.