Don't obsess on the sweets. This is reality and you are a real person, not an anime character. Unlike L, you can gain weight or get cavities from adopting his diet. Unless you brush your teeth a lot and have high metabolism.
You may lose some friends, which is proven by the fact that L has no friends of his own. He even says sadly at one point to Light Yagami that Yagami is his first and only friend -- and this is just a lie so that Yagami will trust him.
Keep snacks handy at all times, L almost always has something sweet (doesn't have to be) nearby and handy.
Unless you actually are a genius, do not attempt to solve crimes in your area.