That’s pseudoscience.

Regardless of any minor variability in metabolism, you literally cannot get fat from things you don’t put in. This is like high school or middle school physics. This is by far the biggest factor in obesity (consumption).. such that everything else is essentially irrelevant. People with actual metabolism disorders either die or require replacement of enzymes, whether that’s type 1 diabetes or the rarer metabolism disorders.

If you eat high volume foods with calories at or below what you’re expending, you will not get fat, full stop. Starving people aren’t fat.

There are of course behavioral differences that dictate consumption, some of which are genetically influenced, but metabolism has not much to do with it.