How to make something disgusting?

I love chocolate. How can I make it disgusting to myself? My brother loved to eat cheese but one time he puked after eating a lot of cheese and he was disgusted by it ever since! How does this happen? Its very interesting and I want to make an experiment for school by becoming disgusted by a food i like! Any ideas? An example of a food i simply cannot ingest is liver or blue cheese. thx xD