Just a bit of personal experience:

I looked into the Atkins/Paleo diet after Yudkowsky mentioned it, and the arguments were convincing enough for me to give it a try; I've switched to eating mainly vegetables and meat for the past couple months, with the occasional high-fibre bready thing thrown in (the fibre allegedly prevents the blood-sugar spike you get from carbs).

I am now back to my Summertime working-out waistline, despite pigging out on bacon-cheese rolls and being lazy as all hell. I feel healthy and fine - though I do miss carbs - and my muscle-mass is easier to generate, and has greater longevity.

I'm unable to locate the original post, but what Yudkowsky argued was that lack of rationality could lead to mortal effects, such as the politically-founded 'recommended diet' we've all been raised with; the history behind the food pyramid is more than a little suspect. I'd heartily recommend this diet for the rest of you (also, this diet should be a major consideration for present obesity levels).