Thanks! I'll go ahead and not update.
Unfortunately, I feel a little smug about not updating, and Eliezer has pointed out that, to avoid confirmation bias, you should only congratulate yourself when you do update your beliefs. So I'll try to have LW pick apart the next pro-Atkins study I see too.
This seems like an authoritative 25-year research project that the Atkins diet is pretty bad:
http://www.nutritionj.com/content/11/1/40/abstract
Right now my belief is that the Atkins diet is good. It's backed by anecdotal evidence of trying a low-carb diet for 18 months following a 12-month low-fat diet and seemingly getting better results with the low-carb diet.
I'm counting on LWers to tell me how to update my belief in light of this study. Thanks.