Is it normal my son eats double his caloric intake and isn't fat?

My son is 14 years old, slightly taller than average, average build. He eats like a beast, he wolfs down every meal, he always asks for the leftovers and then eats junk food and drinks soda afterwards, he'll take up a 2 litre bottle of coke to his room (regular, he refuses to drink diet) and by the time he brings his dishes and washing down he'll bring the empty bottle with him too, I'll list his favourite foods and the stuff he doesn't go near, this is what he doesn't eat;
Red meat, says it is tasteless and bad for you
Diet soda, says it gives you cancer and it tastes bad
White bread, same reason as the diet soda
Vegetables except for potatoes, hates crunchy food
Solid fruit, same reason as above and the seeds are annoying (he drinks the juice like a maniac though)
And this is what he has described to me as his favourite foods
Chicken (he'll eat no matter how it's cooked)
Pork (pulls all the fat off though)
All fish except salmon and tuna
Pasta with either cheese or various herbs, he says it tastes like KFC that way
And his favourite, a brown bread roll with the following;
Bacon
Chicken
Boiled potatoes
Ketchup
And I don't even know what crazy combination of garnishings he puts on it.
2 days ago I checked roughly how much calories he ate that day by checking the labels on the stuff he ate/drank, I got 5800 roughly, and then I realised the recommendation is 2000, I had a high metabolism when I was younger but nothing like this, my wife used to be fat when we were younger so he doesn't get it from her, I'm genuinely worried for him, not because of his metabolism because it appears to be in ultra mode but because he doesn't gain any weight, he isn't fat at all, he isn't that muscular either, he always complains about pains in his wrist and ankles so he may have clogged veins, I'm definately taking him to the doctors this week, there is definately something wrong with him.