When someone who was previously a fat/unattractive child loses weight or "glows up" and overcompensates for their past insecurities by acting out. Usually they end up acting like the same people who bullied them growing up.
Friend 1: Emily lost weight and now acts like she's better than everyone.
Friend 2: classic Former fat kid syndrome.
by 1234456hjk July 22, 2020
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A person who, in the past was fat and/or utterly unattractive, but now is considered attractive by society, yet still retains the mental, and emotional status of a fat kid and therefore does not understand social cues.
"Jane may be hot now, but she still suffers from FFK Syndrome or Former Fat Kid Syndrome"
by 1122 February 5, 2009
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