If you want to lose weight then consume less calories than your body burns. It really is that simple. Yeah, you probably won't be comfortable, but that's the trick to losing weight. You could do it eating nothing but Twinkies, you won't be healthy, but your weight will drop.

Surprised to see that this article mentioned "portion" or "serving" a total of zero times. That's the trick with cereal. Taking cocoa puffs as an example, 50g of them is 200 calories. 50g is probably 4 spoonful's (no source just my opinion).. very little, if you just pour an amount that looks good to you into your bowl, yeah it's going to easily add up to an 800 calorie meal when you add milk.

I would agree that it's deceptive, but you can't blame them for making you fat. All the information you need is right there on the label. This is just for managing weight, getting proper micro and macro nutrients takes a little more research.