Are there proven ways to help prevent endometrial cancer?

Possibly. There are no proven ways to prevent endometrial cancer, but there may be ways to decrease risk. Estrogen-only pills and being overweight increase risk. There are also hereditary factors. Weight loss (if you are overweight) combination contraceptives, increased physical activity, low fat, high fiber diet may lower risk. See http://www.Cancer.Gov/cancertopics/pdq/prevention/endometrial/patient.
Yes and No. There are known risks for endometrial (uterine) cancer. Some drugs like estrogen and tamoxifen. Family or genetic predisposition obesity less: hypertension and diabetes mellitus ? Ultrasound and gyne follow up are recommended for high risk patients. Hysterectomy is an option fr those who had their children, .
Not prevent, but. Early detection. Endometrial cancer is common, and usually detected on annual exam. Unlike cervix ca, where a virus causes most cases, and it can be prevented and detected with annual pap, we do not have a cause endometrium. The outlook worsens with delay, cell type, and penetration into the underlying muscle. Unusual (heavy, post menopausal) bleeding is a cardinal sign.