Okay, the dairy was one I was going to suggest. Can I suggest trying to not eat gluten? I had a blood test years ago for celiac disease and it came back negative, but about a year ago I decided to stop eating wheat... and it just seemed like one day I realized I wasn't sick anymore. I now know if I eat something with wheat, there's a threshold somewhere of how much is okay and how much will make me sick. I don't know what it is, but by and large I just plain avoid wheat. I actually used to have trouble with dairy, but since axing gluten I am fine with dairy. That said, a lot of people have issues with dairy, so if you already know it causes issues, I'd probably still avoid it. The processed packaged foods probably aren't doing you any favors, especially as you will start to expect more from your athletic performance, and gluten will be hanging out in a lot of those. If it's a big deal there is a brand of gluten free processed foods, I want to say it's Amy's? You can trying switching to those. Stick it out for maybe a month or so and see if that doesn't help? I don't think your calorie content is high. It may be a bit low from the athletic perspective even. But I think the first thing is to try and care for the IBS as much as possible.