Someone reportet the bug in a german bug thread:
Sometimes it happens. He's eating some food and than it happens.
His Minecraft is giving his user once again a food item. But he's not right-clicking, also there aren't any particles of the food.

Normaly while you right-click with a food item you only eat it, only at the moment while you click.

But the Minecraft of him gave him more food than he want to.

I don't know how to reproduce it... It just happens sometimes.

Some users had this bug in 1.3.2 too.