Why is it that very many people who were skinny pretty kids grow up to be very fat and most of the fat kids lose weight?

Am I seeing a pattern?
Most of the skinny kids are fat as heck now, I hardly recognize them. Even I was a fat kid but now I'm borderline skinny. Is it like a metabolism thing?
I notice this trend is prominent.
Case in point,

do fat kids become skinny adults? | Yahoo Answers


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Published Dec 04, 2013

All my fat friends from school literally ALL of them are now skinny years later. So do fat children become skinny adults?!


Skinny Child. Fat Adult. | Fifty and Fat


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Last updated: Jun 02, 2014 ·
First post: Jun 02, 2014

Skinny Child. Fat Adult. June 9, ... when I was a kid I played outside. ... My fear of becoming pregnant again won out and I gave up the cigarettes.