Check out the link I posted earlier.
Feeding causes their organs to swell which is taxing on their system.
One appropriate sized meal (if that is one item or two smaller items that make up the same amount) causes one digestion period.
One smaller item fed more often means they are having to go through the digestion process more often. The organs (heart, liver, etc) swelling up and going down much more often.
I hope that helps explain?