Honestly, so many people out there choose a suit which does not match their body type. Now, if the groom is nice and tall with a slim figure, most things will look great on him. However, if he is far too skinny, then you want to opt for a double-breasted suit. It creates the illusion that there is more bulk there.
If the guy is erring on the heavier side of things and wants to give the impression that they have slimmed down, then make sure they get hold of a fitted suit. A person that wants to slim down should not opt for lighter colored suits. They will have the opposite effect. Instead, you will want to opt for darker colored suits.
If you are short, then opt for a suit which has fewer buttons. The more buttons, the more it shows off how short you are. Two or three buttons on your jacket should be sufficient.