borofergie said:
I'm not sure that anyone, including Taubes, thinks that you can get around the First Law of Thermodynamics (conservation of energy). I remember him writing about extensively in GCBC: if you eat more calories than you expend, then you will gain weight. This is a scientific fact that no-one disputes.
I'm in the middle of trying to read Gary Taubes's enormous tome "The Diet Delusion" and have just read through the section where he talks about researchers using statements about the FIrst Law of Thermodynamics as a means of avoiding a scientific investigation of the notion that low fat diets might not be the best way to lose weight. To be honest, what he says about the First Law is a little confusing - and I don't think it is very well written.
We should all remember that the FIrst Law of Thermodynamics is about conservation of energy - not about gaining or losing weight. The FIrst Law, in its simplest form says that the change in energy in a system is equal to the energy added to the system minus the energy lost by the system. It simply is not true that this mandates an increase in weight for a system that gains energy. A simple (fictional) example will, I hope, clarify what I am trying to say here ......
I have a shed in the garden. Amongst lots of gardening tackle, cans of paint & other rubbish, I kept about 100kg of timber logs in the shed. The calorific value of the timber is 14,700 kJ/kg - so the 100kg that I store there has an energy content of 1,470,000 kJ (equivalent to about 350,000 food calories). As it stopped raining this morning, I decided to do a bit of tidying up. I removed the 100kg of wood from the shed and built a bonfire with it that I will light this weekend. I did some tidying in the garage too. I remove three 20 litre jerry cans full of diesel that I bought some months back when some clown government minister said something daft about fuel shortages and it being sensible to stock up. I put the jerry cans in the shed. They weighed a total of 50kg (excluding the cans themselves). Now, diesel has a net calorific value of 43,400 kj/kg - so my three jerry cans contain 2,170,000 Kj (equivalent to 516,666 food calories).
So what happened here? Well, I added 516,666 food calories to my shed and removed 350,000 food calories - so to satisfy the First Law, my shed must now contain 166,666 more food calories than it did before (it's had a humungous meal!!). So, did my shed gain weight? No, not a bit of it - I added 50kg but removed 100kg. It got 50 kg lighter!!
After reading much of Gary Taubes book and thinking about the implications of the FIrst Law of Thermodynamics, I came to the conclusion that any nutritionist or diet researcher who quotes the FIrst Law of Thermodynamics at you, as a justification for rubbishing the results of trials that conflict with his (or her) preconceived notions is, at best, guilty of wooly thinking and at worst .............
Andrew