If he's that busy, help him out by preparing a meal. It saves him time and stops him from ordering or grabbing crappy food to save time. It forces him to take a break to spend time with you and eat. Just don't be too particular about when you eat. Sometimes you can stop in the middle of engineering work to take a break without issues, and sometimes it's like stopping in the middle of juggling ten plates and it's better to just finish the problem. Don't be miffed if the food gets a bit cold while he gets to a good stopping point.