A calorie is a calorie!

Is a calorie a calorie?
Andrea C Buchholz and Dale A Schoeller
Wanted to post this here for my own organization.  This review looks at the results of various studies comparing high protein (OK, OK, yeah Atkins is high fat not high protein ...) low carb diets to low fat.  Their ultimate conclusion is, basically, yes.
Given the Eades/Colpo dust-up over at their respective blog/sites, this whole thing has come up again.  I think it's important to remember that food calories are a measure of metabolizable energy.  The 4/4/9 P/C/F numbers are averages that were determined for mixed meals.  But this should be accountable for in excretory products, because not only do we have thermodynamic laws, there's ultimately a conservation of mass issue.  Changing the proportions of macronutrients doesn't change the way(s) they are metabolized, though in the case of protein its use is changed.  A fatty acid that goes into the fatty acid spiral will produce the same amount of ATP whether or not carbs are around.  If it didn't, then there would be some FA fragment floating around that has to go somewhere.  The only macronutrient that seems to change in the presence or absence of carbs is protein.  Protein is thermogenic.
If a metabolic advantage exists, it would show up consistently, and increase with time.  As pointed out in this study, most of the extra weight loss at 12 weeks was already accomplished at 6 weeks (and could be attributable to water weight).  Furthermore, the Atkins trajectory for weight loss in one famous comparison study, "The  A to Z Weight Loss Study" is in the opposite direction from 6-to-12 months.  See below (click to enlarge)

I'm not sure if this is statistically significant, but if you look at Atkins vs. Learn, most of the difference is in the 1st two months and after 12 months, the difference is not much more than it was at 2 mo.  Further, if there's a significant advantage at 2 months, one should see that difference in loss triple for 6 months, and be 6X as great at 12.  This clearly doesn't happen. 

In most studies, it is degree of compliance to any plan that correlates best with weight loss.  It just so happens that LC's less structured plan and appetite suppression of protein assists greatly in this endeavor.