Out of 13 times I took planes (mixed airlines)
13 times in economy class
4 out of 13 times heard people ask for 2nd helping
3 out of the 4 times answer is "If everyone had theirs and there
is any left, we will give it to you"
1 time, a lady beside me was sleeping and didnt want her meal,
so when the stewardess came to clear, asked me whether I would want
her. I decline as I already quite full.
I believe normally the steward/stewardess will give you if they
can.