What I personally would be worried about is the long-term effects. Unfortunately, these would be very hard to pinpoint as it would be virtually impossible to get enough people to volunteer eating a certain diet, without much fluctuation, for some 30 years or so. And even if such a study would happen, the endless argument would start: "But the diet A contained X, and diet B lacked Y, so obviously we can conclude ..." etc.

Not overeating (and undereating) is like 10 times more important than what you eat, as long as you get enough of all the nutrients you need.

This may or may not be true, and also we could argue about the factor forever. I would say it's way less than 10, especially in the long-term, but I have no way to prove it of course.

Don't obsess over what you eat until there is clear evidence. Eat things you like to eat.

Well, there is the "classic" - "Nutrition and Physical Degeneration" by Weston Price. (Available online at http://journeytoforever.org/farm_library/price/pricetoc.html) He traveled around the world and watched what happened to primitive societies when they introduced western foods in their diets. I read it briefly, and he made an emphasis on dental health, but literally introduction of white flour, sugar, polished rice and canned food produced a huge drop in dental health.