That was never the claim. Nice attempt at a straw man though. You seem to be under the impression that body fat only accumulates in scenarios with excess calories. That's explicitly wrong. What some of these metabolic disorders do is prioritize the accumulation of fat from calories over sustaining other parts of the body. There are multiple ways that your body converts calories into energy, and they can be thrown off by hormones. Some metabolic conditions, like Cushings, overstimulates the production of body fat starving the muscles of energy so they atrophy.

To put it in clearer terms, you could take two people of identical sex, height and weight and feed them the exact same diet with the exact same exercise routine and still have one pack on more body fat due to hormonal issues impacting how they metabolize food. Telling the person who's gaining fat to just eat less isn't helpful or healthy. They need to address the condition causing the additional body fat accumulation and it's not excess calories.

To be perfectly clear, I'm not suggesting that this is the case with microplastics. I don't think we have the research to determine that yet. I'm merely disputing the inane "just eat less bro" nonsense that tends to crop up in these threads.

> I'm very skeptical. I think there are some things that may make us "feel hungrier" but there's nothing changing our metabolism.

> If we are to believe this, it would mean that "plastic" is making our bodies so much more efficient that there's extra energy that's being stored as fat.

I think it's likely the opposite, e.g. there's something (not necessarily plastic) throwing off hormones, so the body ends up storing more of the calories as fat than it would if it was healthy. It's not at all clear (to me, at least) that a healthy human body would continue to store fat indefinitely, regardless of how many calories were being consumed.

This assumes 100% of energy is absorbed from food which isn't true as far as I know.