For those saying that "kick starting metabolism" is a bit woo, and a bit nonsense, you have to think of your body like an engine (which it sort of is). Food is fuel, and regularly putting fuel into a car keeps it ticking over nicely and keeps the engine running.
When you wake up in the morning after hours and hours and hours of inactivity, you need an injection of fuel to get your body functioning at an optimal level. If you don't give your body fuel, it's like trying to run an empty car on a cold day - difficult, heavy, cumbersome and spluttery.
It's been proven scientifically for a number of years now that the longer your body goes without food, the less like it is to expect food, and it turns over into "starvation mode" - so, the next time you feed it, instead of burning the calories it gets, it stores them as fat in order to get through the next period of "starvation" when it comes. When your body gets fed regularly, it never needs to cling to the calories as it always knows more are coming.
Also, eating breakfast and then wanting something else mid-morning is not a bad thing!! It's a sign that your body is working effectively. Mid-morning and mid-afternoon snacks are very good for you unless the snacks comprise 3 Flakes and a slice of cheesecake