Gwen has a VERY good post up (while she's busy traveling, it's a guest post) about weight regain. It, in conjunction with Tom-the-FatHead's current experimentation with resistant starch, made me remark to myself that it's easy to see why people regain the fat they so painstakingly lost! You see, the most obesogenic foods are SNEAKY -- you don't notice the damage they do until it's done.
Some of us have been able to heal decades of damage through eliminating the elements that wrought the havoc. Paleo-type elimination diets are outstanding for this, as was Donaldson's "strong medicine" regimen of getting off the "allergy bandwagon" -- the list of foods with which most of his sensitive patients had trouble. Eating simple foods which the majority of "western" people can consume with impunity, for long periods of time, gives our bodies a chance to do what they were designed to do -- heal itself. Cleaning up deleterious habits like shorting ourselves on sleep and getting outside for sun and air help.
Humans are infinitely curious, like the monkeys and rats to which we're distantly related, though. We can't resist the temptation to TWEAK. We live to expand our horizons! We are extremely attracted to novelty. ...We can't leave well enough alone.
I'm not going to suggest anyone stop experimenting, because that's how we progress. I WILL, however, warn against the insidiousness of the "neolithic agents of disease." Just because i don't feel bad results from one small exposure to wheat or nightshades doesn't mean that little bits of damage aren't happening below the level of perception.
If we go back to the diet which got us into trouble in the first place, it's like falling for the half-truths of the popular media. "Oh, one little bite won't kill you!" may be true, but it certainly won't benefit you in the long run.