The Houston-based duo known as "The Art Guys" did a year long project called "bulk up for CAM" (Contemporary Art Museum), in which they went from flab to fab in time for a retrospective of their early work at the museum in question.

Their site has a before and after:

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And this article has a description of their oatmeal and egg white-heavy routine of diet and exercise:

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They did this in 1994-95...I wonder how quickly they reverted back...