Yeah, intervals burn 100% glycogen/carbs since they're so intense. It's actually possible to deplete your body and bonk much faster doing intervals than anything else; in less than 90-minute ride. Doing this a lot makes your body thinks it's in scarcity and famine and will start hoarding fat. You have to make sure you eat enough during and for recovery, but not so much that you get extra calories. It's a numbers game.