She'd say she hardly eats anything and has thyroid issues.
There may be some truth to it, but I wouldn't rule out some other form of stupidity causing the issue.
I knew a fatty with thyroid issues. She had been on thyroid medication for decades and couldn't lose weight regardless of what she did.
Turns out she is meant to take the medication on an empty stomach first thing in the morning with selenium for better absorption. But this fatty was taking it after eating her breakfast and basically her body wasn't absorbing any of her medication. She managed to lose 50lbs in a year after I got her to change that and BSed her with some diet changes and charged her a minor fortune for it.
What's even more shocking is that she has a biochemistry degree, but too fucking lazy to check how to take her medication properly.