I do eat 20-30 bananas in one meal, no typo. It fills my stomach. But fruit is mostly water, and digested quickly, so I can go for a 2nd run about 6 hours later.
Having such a large volume of food in one meal takes practice; your stomach gradually stretches out. Most people who start will eat 5-6 fruit meals per day, but then gradually increase their size and decrease their frequency.
In Doug Graham's 80/10/10 program, he suggests:
-a minimum of 80% of calories from carbs.
-a maximum of 10% of calories from protein.
-a maximum of 10% of calories from fat.
Most fruits have a ratio of about 90/5/5, and most leafy green vegetables are more like 70/15/15. Eating both, you naturally get around 80/10/10.
You don't need a lot of fat or protein. The amount you get on this plan is sufficient. On his plan, you can eat fatty fruits (avocados, etc.), nuts, & seeds, but you are not supposed to go above 10% for protein or fat (so highly concentrated fat sources need to be a small part of the diet).
And no, I fart less than I did on the standard American diet. Why? Because fruit is easy to digest, and moves through your system quickly. My bowel movements are also very regular. But if you mix fruit with something which moves slowly (like meat), then that can lead to problems.
Try it for a week or two. See how you feel. My running has never been better.
But I am not the expert. Check out the links above, or get the book.