What do thin people do to get that way if they don’t exercise and diet?

I have a very skinny cousin who eats at high end restaurants and has the same lifestyle is everyone else, but she is skinny like Reese Witherspoon. My other cousin also eats crazy amounts of tasty food and is skinny like Hailey Bieber. My two female cousins that try to lose weight are normal, Jessica Simpson sized girls.

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I mean the legally blind version of Reese, not her current age
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Legally *Blonde
What do thin people do to get that way if they don’t exercise and diet?
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