Paul, I think you are confusing the issue by talking about the astronaut “getting younger”. My understanding is that relativity maintains that her ageing process would be slower, relative to someone stationary on Earth. At no time would the astronaut become younger than she had been at a past time. You will probably point out that you didn’t say that would happen, but “getting younger” implies just that, unless you are more specific about what you mean.

The eating problems you mention would not apply, because, for the astronaut, time would pass “normally” (1 sec per sec). In her RF it would be time on Earth that would be passing at an abnormal rate.

There never was nothing.