Are steroids tax deductible if you are a professional bodybuilder?

[gib]

In theory, if you file Self-Employed with athlete as your occupation, they are a legitimate expense.

Correct.

[oldgolds]

Say if you win the Olympia, receive a 400k paycheck. If you took 100k steroids to win the title can you then lower your tax base to 300k?

No, but you'l probably die young so you will save on taxes over the long run.