The western world is full of overweight people desperately trying to starve themselves thin. They clearly can't do it. Hunger is as overriding a drive as sex, and trying to resist it is impossible for normal people. All you'll manage to do by cutting down on what you eat is to make yourself permanently hungry whilst eating exactly the same amount. As well as the hunger you'll manage to store up vast feelings of self-loathing about your lack of willpower.
I think we all know grossly overweight people, usually women, who really, really want to be thin, but would settle for 'not grossly obese', or even 'a bit less grossly obese'. These poor people are forever eating single salad leaves instead of proper meals, and their reward is that they feel appalling because occasionally their hunger gets the better of them and they wolf down uncontrollable amounts of food. You would too, if you were in their constant state of semi-starvation. It would be like trying to torture yourself to death.
Their reward for this is to be considered weak and greedy by the less afflicted portion of the population. They get fatter and fatter and are in a permanent state of misery and self-loathing. Pity them.
Exercise doesn't seem to help much either, for the simple reason that if you exercise, you get hungry to match. It will make you fitter, stronger, happier (as long as you don't take it too seriously), and has a host of other benefits, but it won't make you lose weight. In fact since muscles weigh more than fat, exercise will make you weigh more (but look better). It is, in moderation, entirely to be recommended, but not as a technique for weighing less.
In fact, let's get one thing clear here. Losing weight in and of itself is not interesting. Most people want to lose fat. Most men would actually rather have more muscle mass.