Did you see Mark's interview on the Diet Doctor's website? If not, you should because it's a great interview. In there he says he never had trouble with grains either until he gave them up and then felt incredibly so much better. He just never knew.
I was like that, too. I didn't have any trouble at all and still don't. But if I eat them regularly, I lose my feeling of vitality. I don't get IBS like Mark, but I get generalized inflammation and pain and I just start feeling like all these older people around me complaining about their shoulders and their brain fog and having to turn down activities and things. I believe my poor boyfriend has IBS from grains but he's opposed to this diet like you.
I ate fairly badly as a child, but they didn't have the HFCS yet. I did eat a lot of sugar. I had a lot of allergies as a young child, with acute immune responses like hives, that I assume I grew out of. None were to grains but I was not allowed to eat bread because of the yeast. I was allowed to have hard tack or bisquick biscuits.
Female, 5'3", 49, Starting weight: 163lbs. Current weight: 135 (more or less).
Starting squat: 45lbs. Current squat: 170 x 3. Current Deadlift: 220 x 3