Richard over at Free the Animal has done all of the donkey work on the latest TEE study. I'd just like to add a happenyworth.
Dr Micheal Eades in 2007:
"...what we’re talking about as a metabolic advantage is at the max about 300 kcal per day."
Ludwig's group using stable isotope doubly labeled water for Total Energy Expenditure assessment in 2012:
"During isocaloric feeding following weight loss, REE was 67 kcal/d higher with the very lowcarbohydrate diet compared with the low-fat diet. TEE differed by approximately 300 kcal/d between these 2 diets..."
I'm no great fan of metabolic advantage arguments. I like uncoupling proteins and the way that feeding electrons in to the respiratory chain at the FADH2/CoQ couple is significantly less efficient than feeding them in as NADH at complex I. Calories out can be in to heat (or in to adipocytes if you are so inclined). Your body can't harvest heat from the respiratory chain. We radiate that. There is a modest emphasis on NADH production from glucose and on FADH2 generation from beta oxidation... They feed in differently.
There have been some ugly arguments on the net over the years about metabolic advantage. Eventually the numbers give you some sort of idea as to who is correct and who is talking bollocks.
Quite why fat metabolism should be intrinsically more thermogenic than glucose metabolism is very interesting. Maybe there will be time to go in to this some day. But I live with a core body temperature at well above ambient, most of the time.
But for now, I simply find the number match between 2007 and 2012 rather gratifying.