It's not just the "feeling better after eating", but that the health bar isn't calculated on the single appearance of that line. I'm too bad (and lazy) with math to sit down and calculate it exactly, but let's say the health bar's depletion notches are at 90, 95, 100... if your villager's health is at 91, then 8 times feeding gives him 4 points, which then moves the bar from the 90 notch to the 95 notch.
That probably isn't it exactly, but you get the general idea....