A calorie is a calorie is a calorie; so we're told.
Calories in - calories out matter when it comes to our weight; so we're told.
Eat less and move more, reduce calories and increase calories used, the secret to weight loss; so we're told.
Back in 2004, Drs. Feinman and Fine offered up a paper, published in Nutrition & Metabolism, "A calorie is a calorie" violates the second law of thermodynamics.
Within that paper, it was noted that, "A review of simple thermodynamic principles shows that weight change on isocaloric diets is not expected to be independent of path (metabolism of macronutrients) and indeed such a general principle would be a violation of the second law. Homeostatic mechanisms are able to insure that, a good deal of the time, weight does not fluctuate much with changes in diet – this might be said to be the true "miraculous metabolic effect" – but it is subject to many exceptions. The idea that this is theoretically required in all cases is mistakenly based on equilibrium, reversible conditions that do not hold for living organisms and an insufficient appreciation of the second law. The second law of thermodynamics says that variation of efficiency for different metabolic pathways is to be expected. Thus, ironically the dictum that a "calorie is a calorie" violates the second law of thermodynamics, as a matter of principle."
While the paper has been cited a number of times over the years, no other major study or paper has challenged the idea that weight loss is mostly dependent on "calories in calories out" - so lacking is any question of this belief that many continue to hold the not-so-subtle idea that if someone isn't losing weight on a calorie restricted diet, then they are not restricting calories enough or they're cheating and just won't admit it.
Well folks, get ready to read an eye-popping study published this month in the International Journal of Obesity, Clinical significance of adaptive thermogenesis. (full text)
In conclusion, based on studies that have shown a greater than predicted decrease in EE under energy restriction circumstances, this review presented arguments in support of the potential of adaptive thermogenesis to impede obesity treatment on a short- and long-term basis, at least in some individuals. In some cases, the adaptive decrease in thermogenesis was shown to be significantly related to a single cycle of body weight loss and regain, an increase in plasma organochlorine concentration following weight loss, and a lower than predicted EE was also shown to be associated with severe nocturnal oxygen desaturations in OSAS. This suggests that energy metabolism might be sensitive to stimuli of different physiological nature and that adaptive thermogenesis could be quantitatively more important than what is generally perceived by health professionals and nutrition specialists. However, from a clinical point of view, several issues remain to be investigated in order to more clearly identify adaptive thermogenesis determining factors and to develop strategies to cope with them. Along these lines, it is concluded that unsuccessful weight loss interventions and reduced body weight maintenance could be partly due, in some vulnerable individuals, to the adaptive thermogenesis, which is multicausal, quantitatively significant, and has the capacity to compensate for a given prescribed energy deficit, possibly going beyond any good compliance of some patients. [emphasis mine]
Weight loss impeded, even with restricting calories and good compliance?
Who'da thunk it possible?