borofergie wrote:Your body stores excess energy as fat. The calorific value of fat is 9kcal/g
That is just school-boy maths - and should perhaps be prefaced by "all other things being equal". Can you cite any real published studies that substantiate that human bodies actually behave in such an idealistic fashion? There are references in the Gary Taubes book to several studies that give inconsistent results, such as folk gaining weight when eating less and the converse. Unless you can explain the reason for such inconsistent results then you are simply kite flying.
You want be to provide references that "the first law of thermodynamics" applies and that the principal mode of energy storage in humans is fat?
I'm stating the conventional position. If you have some alternative theory you should probably write it down...
The First Law of Thermodynamics applies to ALL systems. How is that "kite flying"?
Give me one example of ANY system for which the first law doesn't apply and I'll take you seriously (and also applaud the Nobel prize that you'll pick soon afterwards).
The FIrst Law of Thermodynamics is about energy and says nothing about weight.
Fat is just is the storage of chemical energy. An increase in stored chemical energy is associated with an increase in weight of the system. So of course the First Law of Thermodynamics applies.
The Second Law says that there will be some system losses, and obviously you have to account for waste matter in Eout.
I don't see that the Second Law of Thermodynamics has any relevance to "system losses", whatever you mean by that.
The Second Law of Thermodynamics states that it is impossibe conversion from one form of energy to another with 100% efficiency. When you convert chemical energy "fat" or "glucose" to kinetic energy and thermal energy during exercise, energy is lost through heat rejection. To fuel 3500kcal of exercise you need to burn more than a pound of fat.
If you're going to have a dig at the First and Second laws, it would be a pity not to take on the Zeroth law while you're at it.
andrewk wrote:As you correctly say, "obviously you have to account for waste matter". I have yet to see any serious study that has measured changes in metabolic rate and also the energy in urine, faeces, perspiration, breathing and so on whilst trialing changes in diet composition and calory content. Isn't it true that the lack of such solid science is precisely the reason why there is still disagreement about the effectiveness or otherwise of different diets??
You haven't looked then. It's standard practice to measure the losses included in urine, feces, heat rejection and even sweat, at facilites like this one: http://www.uow.edu.au/health/healthscie ... index.html
Here is one example: http://www.ncbi.nlm.nih.gov/pubmed/3604965
But obviously there are hundreds.
In fact Atwater used bomb calorimeters to manage the energy content of feces and urine in order to calculate the effective calorific values of macronutrients.