This meditation is advanced practice and not for beginners!
(read no further if you are likely to gross out!)
what we use is to first imagine the food in front of you
understand that it is made up of the four elements which are impermanent
imagine what is like seconds after when it is being chewed and mixed with saliva, broken down -like dog vomit
now you know what it is like if someone opens their mouth and shows it to you!
now imagine a plate of that next to the unchewed food
now imagine it going down the gullet into your stomach
there it will get mixed with stomach acid- you know what that tastes like when you get reflux
you know what it looks like after a while when you vomit- you know what it smells like, looks like- compare it next to the food
then later bile will get added to it
then even later it will turn into faeces- remember the look, smell, texture and compare it next to the food
understand that all of the absorbed stuff gets turned into the foul body - solid and liquid components
what you will see is that often people are left with a craving for food even if they manage to get rid of craving for the body- so this specific method if quite helpful when an ariya is practicing for very high stages of the path.