Jon lifts his head to look over at him with the briefest confusion in his expression though he's grateful to have the name for the doughnut. If it's truly unhealthy, he won't eat more than that bite. Most people are often starving in Westeros, and rancid stew is commonly served at Castle Black. Food safety is not yet a concept there. The long term effects of overeating are not commonly seen beyond basic weight gain. Most people don't live very long in a world like that one, but eating more usually means someone has more money and will live longer.

He notes the sparse plate of the other person, and he can guess as to why.

"...you don't trust it?"