Anecdote disclaimer, not giving advice, not a scientist, my anecdotes prove nothing, yadayada.
But my experience pre-McDougall was that I was a relatively thin person who ate a diet high in "healthy" olive oil. I think I didn't gain weight because I was constantly afflicted with queasiness and indigestion, which made me eat less because I knew it was going to @#$*ing hurt.
The thinnest I ever was in my life was when I was a college student subsisting mainly on chocolate bars, ramen, instant macaroni and cheese, and Fritos. Sometimes I had "luxury" fast foods like cheeseburgers or fish and chips. That junk was so toxic to my digestive tract that I could never eat enough to gain weight.
On a starch-based I eat more (in volume) now, and have no ill effects to stop me from eating until comfortably full any time I want. I do eat more often, and consume a higher volume, but what do I care? I am burning up the calories in healthful activity, not in dashing to the medicine cabinet and/or toilet after every meal:).
