It seems to me that he's never actually had time to sit down and eat at a fast food restaurant he's so busy - he doesn't even have friends he hangs out with to go with after school. Its probably his first time eating there, how sad.
Pretty sure he just released that the only thing he has to do while sitting there is eat and relax.
Like not worry about anything or anyone and relex and considering how fat he is now his only time to himself was spent eating and drinking fast food.