Who told you you're not supposed to eat after 7pm? Ignore the articles that say that. There's no actual reason for not eating after 6pm. Your body doesn't know what time it is, and it burns calories the same way no matter what time it is. The only people who shouldn't eat late are people who suffer from acid reflux/heartburn, and laying down too soon after eating can cause it to flare up. I regularly eat dinner after 8pm and it hasn't affected me negatively whatsoever. Plus, considering you're awake from 6pm-6am, that definitely means you can eat. Just eat your meals like you would normally during a day shift, just the times are reversed.