I don't think it's any problem to eat light when you're sick and have NO appetite. I think it's a good idea to get a little in, but no need to push. I was sick a day last week, and had: a fruit smoothie for breakfast, one piece of toast with PB for lunch, and one piece of toast with PB for dinner. And I had to concentrate to get those down. Like I would forget to keep chewing or to swallow, 'cause there was NO appetite. Didn't seem to have any lasting effects

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OTOH, do get in plenty of water.