How do you get obese?

I just don't understand how people let their body get out of control like that. I mean its not like it happens overnight (right?) so wouldn't you start doing something about it when you notice that you are getting fatter. This is a serious question because it just makes no sense to me.

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+1 y
And I'm talking about people that are like 50+ pounds overweight, not just a little thick.
How do you get obese?
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