Sometimes I want to avoid oil and oil-related food. How do I remove oil from soup?
The easiest way, is to cool (fridge) it down and remove the hardened fat that should have floated to the top.
You could try doing while the soup is hot by using a shallow spoon and spoon the liquid fat from the top, or use absorbant paper to absorb the fat.
In both cases, it will never remove all of the fat, especially if the soup contains meat or is not a clear soup (like a consommé)
You could use an oil skimmer, such as this one from Amazon. It's essentially a sieve with a very fine mesh, it works as fats are much more viscous than water based liquids so stay on top of the skimmer while the water goes through.
I use one to remove meat-based fat and impurities from broths and soups, although vegetable based oils tend to be less viscous so I'm not sure if it would work as well, although cooling it down will make the fat more viscous.