I've been fighting off a cold so begging off housework in favor of goofing off at my blog today. Lots on my mind so I've been rather prolific!
I get tired of hearing this misstated time and again by both people who should know better and those ill equipped to comment on such matters, but who do anyway. I'll abbreviate The First Law of Thermo as TFLOT.
Calories In = Calories Out + Energy Stored is a fact. This boils down to simple conservation of mass in the end as I discussed in a bit of a rambling post HERE. From hereon out I'll use CI and CO for calories in and out respectively.
The first "error" many are quick to point out is that TFLOT applies to a closed system, and as we all know humans are not closed systems. True enough. But all we need do is expand our system a bit to include our surroundings and voila! We're back to a closed system for the purpose of energy balance equations. But we don't need to even do this for the most part when we realize that the Calories Out term is multifactorial and all we need is to have a term to account for such things as heat lost to the surroundings.
Some of the more thin skinned in the Calorie Denial movement may be offended by Lyle's language, but to date this happens to be the best, comprehensive, layperson-friendly treatise on the web concerning Energy Balance: The Energy Balance Equation by Lyle McDonald. He painstakingly dissects each term and there's really no sound argument against any of his points.
This brings me to the second "error" made most often by Deniers, that conversion of energy to thermal energy constitutes an entropy loss requiring Second Law principles be applied. Ummmm..... NO! The evolution of heat in an exothermic (heat liberating) chemical reaction is dealt with quite well applying TFLOT principles. Energy "lost" to non-conservative forces (e.g. friction) in mechanical contexts is also calculated by simple applications of the energy balance equation. TEF and thermal losses to the environment are handled quite well by the TFLOT. Given as most humans maintain a relatively constant temperature and modern humans live in relatively temperature controlled environments most of the time, this part of our "CO" term remains relatively constant. But, it has been shown that we can lose weight by tolerating periods of shivering cold, and there's nothing in that violating TFLOT, indeed it supports it yet again because it increases the energy we must expend to stay warm.
But what of Dr. Eades ridiculous assertion that if TFLOT held we could gain weight sitting in a warm room? He said that folks, in the comments of one of his absurd responses to Anthony Colpo, I just don't think it's that important to track down the link. Now perhaps there is an organism somewhere on this planet that harnesses thermal energy to "fix" mass and does so, but I'm not aware of one. Plants use radiant light energy through photosynthesis to synthesize larger carbon molecules from CO2 which is probably the closest analogous process, but plants in no way violate TFLOT in doing that. The radiant energy is part of their CI.
When Feinman and Fine, and Eades and Harcombe and myriad others claim we're not at equilibrium with our environment so TFLOT need not apply and thermogenesis demonstrates a need to apply Second Law principles, they are not making sense. We are not steam engines attempting to harness thermal energy to do mechanical work through the expansion of a heated gas. Thermal energy is a perfectly valid term on the CO side of the equation. And TFLOT is applied to systems that are not in equilibrium all the time!
I've said before and I'll say it again, the whole equilibrium free energy stuff is largely irrelevant in the human body because most of our chemical reactions are occuring far from equilibrium being catalyzed by enzymes whose levels are under hormonal control. And at any given time energetically unfavorable reactions, such as fatty acid synthesis, are occurring because we have the ability to harness energy liberated from one reaction to drive another. It is reasonable to conclude, as well, that if entropy losses occur, these too, are relatively constant.
Bottom line: Heat is not entropy and it is perfectly capable of being dealt with on the CO side of the Energy Balance equation. Since we don't even attempt to harness thermal energy, it need not even be considered in terms of Second Law.
Humans can do a lot of amazing things, but we can't make something from nothing any better than the next species ;-)