I've heard of it before. I think it does happen. Mercury accumulates in fatty tissue, as with anywhere in the body. You drop weight, you drop mercury. Just like yeast contain mercury in the body (if you're poisoned) and sometimes if you aggressively kill it with antifungals, you "can" end up with acute symptoms from the yeast being split open and releasing their mercury.

Though yeast causes enough issues on it's own and has got to be dealt with, or it can push a person over the edge. I use diet to do that.

Also, you may need to build yourself up with healthy fats and proteins, like eggs, meat and good fats like butter, lard, extra virgin olive oil, organic coconut oil etc. These help the body alot. They encourge bile production (need for toxic elimination), they encourage release of some mercury, they help repair/build tissue etc. Fish oil is good to have on top of this (cod liver oil).

As well as eliminating sugar, yeast, gluten grains and possibly milk and fruit and potatoes (natural sugar).

This can help a lot of people enormously.