Well, I am currently a 38 year old overweight (roughly 250ish) person who is working on changing up diet to get back to 200-215-ish like back in highschool/college).
I've spend my entire life eating sugar cereal- mainly Frosted Flakes, Fruit Loops, Trix, and Lucky charms. And not the recommended serving size of 1 cup- I'm talking a complete fill of a relatively deep bowl- probably at least 2-3 servings there. Plus, I'd dump a ton of 2% milk on top AND have a big glass of the same milk for my drink.
I've since cut that stuff out, and instead eat two eggs every morning first thing, and then usually a banana later morning to keep me full until lunch. I accompany both by drinking lots of water, which really does keep hunger in check.
As such, that's total of roughly 300 calories which isn't bad for breakfast. - The eggs are good for protein and nutrients, and the banana provides potassium and other benefits that give energy.
The problem with the sugar cereal- is that like anything sugary- its a burst of energy, then a big let down, and feelings of hunger later- despite all the food you ate. Ironically the Trix cereal I've been eating most recently probably isn't that bad- only 180 calories per serving + 70 cal for skim milk- but again, I was eating way more than one serving- which probably isn't all that "filling" so that's why I recommend the eggs/fruit, plus lots of water.
As such- I strongly recommend eggs- highly nutritious/filling, and always delicious- combine it with some kind of fruit- a good "sweet" substitute that is natural, and breaks down good in the body unless processed sugar products which just go to the belly.