Saturday, February 25, 2012

The Calorie Gang Proves A Calorie Is Not A Calorie

Even taking the conclusions at face value, the authors found, as other diet comparison studies have, that weight loss or, in this over-feeding study, weight gain, was not dependent on calories alone: “a calorie is a calorie” not.  It is likely that this was what the study was originally trying to disprove and the results must have been a disappointment.  The way out was that, in this particular case, the differential weight loss showed up in difference in lean mass, rather than in fat mass as has been found in other studies showing variable efficiency.  Since 5 % is very low protein it is probably not surprising that the diet could not provide enough protein for an increase in lean mass this group.
In other words, as previously reported, the same caloric intake with a variation in macronutrient composition did in fact produce a different outcome in total mass, with the high protein group, predictably, having the relative benefit of greater lean body mass after the over-feeding experiment.

The author continues:
The reduction in weight found in studies comparing low-carbohydrate diets and low-fat diets not only shows a difference favoring carbohydrate restriction but the improved weight loss is preferentially fat over lean mass. For example, Volek, et al. compared a low fat with a VLCK and the results are as shown below.  In their study, subjects were randomized to one of two hypocaloric diets, a very low-carbohydrate ketogenic (VLCK) diet (carbohydrate <10% of energy) or a low fat (LF) diet and after 8 weeks switched to the other diet. Reported energy was slightly higher during the VLCK but the VLCK group lost more weight and as shown below predominantly in fat, total fat loss, and trunk fat loss for men (despite significantly greater energy intake). The majority of women also responded more favorably to the VLCK diet, especially in terms of trunk fat loss the ratio of trunk fat/total fat was also significantly reduced during the VLCK diet in men and women.  These studies depend on diet recall so are less accurate than the JAMA study but because of the better experimental design, the changes are bigger and with appropriate correction make a less ambiguous case than the JAMA study. The more accurate measurements in the metabolic chamber suggest that individual variation is real and not just due to random error.

In short, the concept that burning a macronutrient in a sealed chamber to determine that macronutrient's absolute caloric potential is of course not the last word in what the impact will be when a human ingests the macronutrient.  Once one thinks this through, the "a calorie is a calorie" idea seems absurd.

But as the author points out at the end of the article, careers and reputations have been built on the "calorie is a calorie" mantra, unproved as it remains, and that will drive research which tries to confirm the strongly held beliefs the "calorie experts" have been preaching lo these many years.

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