It is healthier to burn fat for fuel, Mark wrote at least one long post about it. But my understanding is that, as long as you are metabolically flexible, there's no reason you should have to cut out carbs completely to use fat for fuel. Personally, when I was eating around 4500 calories a day it was impossible without large servings of starch at each meal. My guess is that if you are active enough to need 4500 calories you are active enough to handle, or maybe even require a lot of carbs. And definitely more protein.
Here's roughly what my diet was when trying to gain:
Breakfast: 6 eggs, 1/4 pound meat, bowl of white rice (cup and a half maybe), black coffee
Second breakfast: 6 eggs, 1/4 pound meat, bowl of white rice, big salad (naked)
Lunch: 1 or 2 Baked potato (depending on size) with melted cheese, 8 oz meat, many vegetables
Dinner: 2 pieces of fruit, 8 oz meat, giant salad w/ olive oil + balsamic vinegar
each meal was about 1000-1100 calories and then I took 10g of fish oil and experimented with protein shakes at different times of the day (before bed, after lifting, etc). The total was about 250g carbs, 300g protein, 250g fat. Obviously your choices will be limited by food availability, money, which foods make you feel good, etc. but that's what worked for me.
Have you heard of Dan John? I personally think his perspective on mass building is the healthiest and most practical that I've heard. If you really want to get serious, he has a book about it. This program worked wonders for me, although I was forced to stop early because my depression kicked in hard.
EDIT: I was also a teenage boy when I did this.