I went to a party recently, and the host provided the food. At the end of the party, there was an awful lot left over, and my understanding is that most of it went to waste.

I had a thought when this was happening: if I was the host, why not keep track of how much food my guests actually ate, and try adjusting the amount of food at my next party to match?

The host was not a rationalist, as I suspect most hosts aren't, but upon researching the issue, it doesn't seem as if there's a widespread solution.

There are charities that focus on "recycling" food waste, and there are plenty of suggestions for how much food to bring to parties of various size, and yet I still have the experience of purchasing/preparing far too much food for parties, and almost every party I go to has far too much food available.

What exactly is going on, and how can it be made better? It seems to me as if this is a reasonably low-hanging fruit - getting people to properly estimate how much food people actually consume at parties in order to reduce food waste. It's the sort of calculation any restaurant with an all-you-can-eat buffet has clearly made in order to determine their price point.

Is this a publicity issue, that people don't realize they can optimize the amount of food they purchase and prepare? Or is it psychological, related to akrasia or a bias? I've been told that a host's greatest fear is that they run out of food, but why? Is the way to attack this problem through exposing that fear as unfounded?

This is one of the first external questions I've considered, since committing fully to instrumental rationality.

I'd like to hear everyone's thoughts on the matter.

Thanks.

TL;DR:

Why do people waste food at parties? Is this a solvable problem?