Why do my upper legs near my crouch chaff in between when i run mostly wearing shorts?

Okay, so I did look this up but NOBODY seems to be giving the correct honest answers and it's getting me aggravated so I decided to ask myself.. Gosh, people. So is it because the shorts materials or straight out honesty because my legs are just to large and literally fat?... Those are the two answers I keep hearing from everyone.. Well actually only ONE person believe it or not was honest enough and not chicken enough to come out and say that yes your legs are too fat, consider loosing weight and it will stop. So I believe that one person is right... Everyone else keeps lying and saying that it's because of the material and how to prevent it. To stop it they need to lose weight!! Pretty straightforward... So am I right? Oh and by the way, of course I'm going on a diet..