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1.
Whenever a person eats an excessive amount of food, even if they are thin. This phenomenon is unexplainable by doctors, but still happens.
Man 1: "I heard that John was diagnosed with Fat Man Syndrome."
Man 2: "I would have never guessed... he's so thin!"
Man 1: "But he eats a hell of a lot!"
by K-cin January 15, 2009
 
2.
Doctors diagnose many teens with "fat man syndrome" because they are injured due to their BMI index that is off the charts. Generally, heel injuries are the most common causing the person to limp like a chodus maximus. Be aware that a person limping might not have "fat man syndrome," but instead chode spasms.
That kid limping looks like an idiot because of his heel; we probably have another case of "fat man syndrome."
by thechodemaster January 13, 2009