http://forum.lowcarber.org/showthread.php?t=473283

The study's come up on the thread above.

Recapping some of my points from the other thread;

This study didn't compare a standard american diet to a ketogenic diet. What it did was first put people on a standard american diet, on the calories it took to put them in calorie balance in a metabolic chamber. Then after a month of this as a baseline, they were put on the ketogenic diet.


Most of the study wasn't in the metabolic chamber it was in a metabolic ward, and according to Hall, subjects burned about 500 calories more a day when in the metabolic ward than when in the metabolic chamber--making what was supposed to be weight maintenance, at least during the baseline standard American diet into weight loss during both the baseline and the ketogenic diet phases. This shows that environment, for whatever reason, had a strong effect on metabolic rate--and you can't rule out that there might be some interaction between environment and diet that would obscure metabolic advantage. Metabolic advantage might occur in free-living subjects on a particular diet, but not under the conditions of the study.

The fact that the baseline, which was supposed by design to keep people at their original bodyweight, resulted in weight loss is a big problem--it means that once people went on the ketogenic diet, they'd already been on a weight-loss diet for a month. This might be long enough for some of the "low hanging fruit" of fat loss to have been already picked, setting up the ketogenic diet phase for a reduce rate of fat loss. But it also might have not been long enough for the people in the study to have experienced very much of the decrease in metabolism that can come after a more extensive weight loss. David Ludwig's study where weight reduced people ate low carb or low fat found less of a decrease in metabolism in people eating low carb--here, the metabolic advantage shown wasn't an increased metabolism in people at their top bodyweights, but less of a decrease in metabolism in people who had lost a fair amount of bodyweight. People going into a study like this are probably screened, to make sure they haven't been recently on a diet, since that would be a major confounder. The people out in the real world, who claim to experience a metabolic advantage on low carb--have not been screened, it's possible that metabolic advantage shows up more in people who have struggled with calorie restriction, had some success but were walking around with a reduced metabolism as a consequence.