Um noch mal die Frage aufzuwerfen, ob eine Kalorie wirklich eine Kalorie ist.
Aus wissenschaftlicher Sicht und unter Berücksichtigung der Thermodynamik ist es wirklich egal woher die Kalorien stammen (also egal ob Zucker, Mehl, Vollkorn etc).

Das einzige (und hier liegt wohl auch der Erfolg von Low-Carb bzw. Ketodiäten) ist die postprandiale Thermogenese.
Die bei einer fettreichen (weniger) und eiweißreichen (wichtiger) Ernährung sehr hoch ist.
Sie beträgt ja immerhin max. 25% und macht eine eiweißreiche Diät natürlich „effektiver“ als eine Standard „Low-FAT 30% mit viel Kohlenhydraten“-Diät.
Ferner mehren sich die Stimmen die einer Low-Carb einen höheren Sättigungseffekt zusprechen, was wiederum ein größeres Defizit ermöglicht.

Mit hohen Gewichtsverlusten (Wasser und Bindung an Glykogen) sind hier subjektiv große Erfolge zu verbuchen.


Conclusions

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.

The analysis above might be said to be over-kill although it is important, intellectually, not to invoke the laws of thermodynamics inappropriately. There are also, however, practical consequences. The seriousness of the obesity epidemic suggests that we attack it with all the means at our disposal. Metabolic advantage with low carbohydrate diets is well established in the literature. It does not always occur but the important point is that it can occur. To ignore its possibilities and to not investigate the precise conditions under which it appears would be cutting ourselves off from potential benefit. The extent to which metabolic advantage will have significant impact in treating obesity is unknown and it is widely said in studies of low carbohydrate diets that "more work needs to be done." However, if the misconception is perpetuated that there is a violation of physical laws, that work will not be done, and if done, will go unpublished due to editorial resistance. Attacking the obesity epidemic will involve giving up many old ideas that have not been productive. "A calorie is a calorie" might be a good place to start.
"A calorie is a calorie" violates the second law of thermodynamics | Nutrition Journal - Mirror @ Uni Potsdam