Obsession - what is it?

「Obsession」という単語の意味はご存知ですか？
中級レベルでも知らないという方が多いこの単語。
中高の教科書では見かけませんが、
実際にはよく耳にする言葉です。

"I'm obsessed with food!"

Recently I taught a lesson on obsession based in
a key text book. It's a level 3 text and surprisingly
many students discover this word for the first
time during that particular lesson. So what does
obsession mean? There are a few meanings. I'll
keep it simple. It means you can't stop doing　
or thinking about something, you are 100%
focused on it, but in a very strong way, an
unbalanced thinking. For example, some people
are obsessed with their weight. They can't stop
going to the sports gym everyday. I knew
someone like that. She went to the sports gym
for three hours everyday. Also, some people are
obsessed with food, TV, the Internet, music
concerts, movie stars, traveling, etc. Do you
have an obsession? My obsession is studying.
I love it. I can't stop thinking about it and doing it.
Perhaps this is a positive obsession. Sometimes
obsessions can be negative. Remember, you can
have more than one obsession.

obsession=〜に取り憑かれること、頭にこびりついて離れないもの
particular=特定の、特にこの〜