Will phytoestrogens (such as soy isoflavones) increase a woman's bodyfat? I have read that they help to lower estrogen levels if estrogen is too high.

I dont know the direct answer to that question, but i do know that phytoestrogens act as a weak estrogen. For this reason, and others, it's used in post-menopausal women to help alleviate symptoms such as hot flashes.

I'm not sure if the estrogenic properties of phytoestrogens are enough to contribute to estrogen-associated fat retention/gain.

In all thy getting, get understanding