I'm no expert, so I'll just post what I do, and what I've learned from my experiences. Keep in mind that what works for some people, will have the opposite effect on others. I have a friend who is 5'10", probably eats around 3000 calories a day, of only carbs, and he only weighs 135 pounds.

I eat 6-7 meals a day, sometimes 8. I consume somewhere between 2500-2900 calories, or 300 over whatever my maintenance level is for the day, which depends on my exercise. Yes, I count my calories. The only meals which I eat starchy carbs are breakfast and post-workout. The rest of my meals are mostly protein, and vegetables. In the last 3 months, I have gotten much leaner, while GAINING 4 pounds.

Before the above diet, I was eating the same amount of calories, but more of which came from carbs. I was LOSING weight, and looking fatter.

In conclusion,

Carbs have an effect on fat storage. Yes, you need carbs, but only good ones. Also, you only need so many, and really only at certain times. If your going to be sitting on your ass for 4 hours, you don't need fast digesting carbs which are going to spike your insulin levels. This combination will lead to fat storage. ESPECIALLY in a positive calorie balance.(Your eating more than you burn.) After carbs are broken down by the body, they need to go somewhere. Your muscles are full of glycogen because you haven't and aren't going to exercise. And your liver will probably be filled up also. Since your insulins levels are high from the simple sugars now, your body is desperately trying to remove glucose from your blood stream. The only place left for it, is in the form of fat tissue. Should've had some protein.