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Cronise got the idea back in 2008 while watching a TV program about Michael Phelps. The coverage claimed that, while training, the 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 209 pounds on his 5â€™9â€³ frame and wanted to get back down to 180.) Something didnâ€™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 98.6.