Amy

If the person who treated you advised you not to eat heavily, they
must have had a good reason to do so?

Food intake (given an unlimited supply of food!) is based on three
things - habit, what we "think" we can eat, and what our body
actually wants - and the latter is the most important one to tune
into - I cant say I do this very well all of the time (understatement
of the year), but its worth checking in on your stomach so you start
to know which of those three is deciding what youre eating.

Best wishes

Andrew