I find myself so incredibly perplexed about why people, moreover scientists, seem to think that a calorie is a calorie and exists in a vacuum.
Water will boil at a different temperature under different atmospheric pressure conditions. What that means in English is that you might expend more or less energy to boil water depending on the pressure/environment.
Without considering how dietary composition does affect:
1) metabolism
2) energy level and subsequent physical activity
3) the relationship with individual genetics
4) the absorption of nutrients that can affect the other three
then interpreting the results is extremely short-sighted and unscientific.
It's like saying that eating the following foods which are around 100 or so calories give the same physical results to our bodies:
1) 8 oz of soda
2) 1 apple
3) 2/3 oz of almonds
4) 1 oz of cheese
Or that eating all your calories for the day at one meal has the same physical effect as spreading it out among 4 meals. It's the same number of calories, right?
That's ludicrous, and particularly why the common belief is that so long as sugar-laden cereal or "fruit" candy is fortified with vitamins, it's still healthy.
Atkins DOES have a metabolic advantage.