Cronise got the idea in 2008 while watching a TV programme about Michael Phelps. The coverage claimed that, while training, the US Olympic swimmer ate 12,000 calories a day. At the time, Cronise was on a diet of 12,000 calories per week. (He was carrying 95kg on his 1.75m frame and wanted to get back down to 82kg.) Something didn't add up. Even if Phelps had an exceptionally high metabolism and swam three hours a day, he still should have turned into a blob. Then it hit Cronise: Phelps was spending hours every day in water, which was sucking heat from his body. He was burning extra calories just to maintain his core temperature of 37 degrees celsius.
Very cool. Insane that Phelps was eating 12,000 calories a day!