Whenever I happen to think about it. Usually right before I portal out of my secure base to go explore dangerous areas. If I'm still in a dangerous area when it starts flashing I eat again. If I'm on my way back home, I don't bother. If it's gardening or tree chopping day I'll still eat but maybe only one or two of the three.

I don't spend all my time in dangerous zones so I don't worry about it that much.