Starchy foods, such as precooked rice or tapioca cereals, can help ease your tummy. Prepare the cereal according to the directions on the box, making it as thick as you can stomach it. Just avoid adding too much sugar or salt, as these can aggravate diarrhea. It's probably a good idea to avoid oatmeal, since it's high in fiber, and your intestines can't tolerate the added bulk during a bout with diarrhea.
Potatoes are another starchy food that can help restore nutrients and comfort your stomach. But eating French fries won't help. Fried foods tend to aggravate an aching tummy. Other root vegetables, such as carrots (cooked, of course) are also easy on an upset stomach, and they are loaded with nutrients.
Cooked white rice is another starchy food that can be handled by someone recovering from diarrhea.