http://www.webindia123.com/news/sho...45711&cat=World

Washington | August 17, 2004 4:23:20 PM IST

Two U.S. researchers are further lending credence to low-carb diets by using the laws of thermodynamics to argue that calories from protein are better for losing weight than those from carbohydrates.

The argument is supported by an experiment conducted by Arne Astrup of Denmark's Royal Veterinary and Agricultural University, Copenhagen which found that those on a diet rich in pork protein burned more energy than the ones on a higher carbohydrate diet because they lost more energy as heat.

According to a report in Nature, Richard Feinman of the State University of New York and Eugene Fine of Jacobi Medical Center in New York are using the laws of thermodynamics: fundamental rules that describe how heat, work and energy change in a system to validate their hypothesis.

Dwelling upon the second law of thermodynamics which says that energy spontaneously disperses if it is not hindered, Feinman and Fine point out that protein and carbohydrate are metabolized in different ways and their energy is therefore dispersed in different forms. When protein is broken down by the body, for example, more energy is released as heat than is converted into chemical energy.

They argue that while a hunk of steak and a slice of bread may carry equal calories, the amount of energy the body actually gleans from them, to fuel movement or store as fat, is different.

"To say a calorie is a calorie all the time is false," Feinman said. (ANI)

Another headline:
"Suddenly - after much skepticism - scientists have discovered bees can fly."

No!! A calorie is a calorie after all.
A calorie is a measure of heat !

danny

A Calorie (kilocalorie) as used in food is a measure of how much heat a food produces when burned in a Bomb Calorimeter. Your body is not a bomb calorimeter. Firstly, the body DOESN'T burn food per se. It works using a complex series of chemical reactions. Energy is released by breaking down various macronutrients (Fatty Acids, Glucose, Glycerol, etc...) into smaller compounds (Pyruvate, Lactate, etc...) This energy is used to build ATP (Adenosine Triphosphate) Molecules, which are then broken down into ADP (Adenosine Diphosphate) and/or AMP (Adenosine Monophospahte,) releasing energy for use by the various muscles in the body. Humans are only able to extract about half the energy in the macronutrients we can actually break down.

http://www.unisanet.unisa.edu.au/08366/h%26p2carb.htm



The above is an image of the first steps of Glycolysis (obtaining energy from Glucose.) In the absence of Oxygen, the Pyruvate would be converted to Lactate, which can later be converted back to Pyruvate and metabolized with Oxygen or back to Glucose for later use. With Oxygen it would be converted to Acetyl CoA and then via a series of reactions is either converted to CO2 (Carbon Dioxide) or used to build Fatty Acids, and then Triglycerides/Fat.

http://www.unisanet.unisa.edu.au/08366/h%26p2fat.htm

Fatty Acids are broken down to Acetyl CoA in repeating series of chemical reactions, and then either to CO2 (Carbon Dioxide) or Acetoacetate (A Ketone Body,) and then to ß-hydroxybutyrate (A Ketone Body)

http://www.unisanet.unisa.edu.au/08366/h%26p2ptn.htm

Protein is broken down to Amino Acids, which may be used to build needed compounds/tissues, or may be metabolized as fuel. Their Amino Group is removed and Converted to Ammonia/Urea, which is excreted via the Kidneys. The rest - depending on the Amino Acid - is converted to Acetyl CoA [which can then be metabolized using the reactions described below or be converted to Ketone Bodies,] Pyruvate [which can be used for energy or be converted to Glucose,] or some other compound.

http://www.unisanet.unisa.edu.au/08366/h%26p2cac.htm

Acetyl CoA is metabolized with Oxaloacetate and Water to produce Citrate (Citric Acid,) which is then put through a whole series of reactions ending up with Oxaloacetate, Carbon Dioxide, and GTP (which is converted to ATP.)

As you can see, that is far more complex than simply burning Hydrocarbons with Oxygen to produce Carbon Dioxide, Water, and Heat/Light.

cc - I think what you are saying is that the body does not always extract a calorie of heat/energy from each calorie of heat/energy inputted. It seems to be true doesn't it - and explains a lot.

I think Dannysk was saying something tongue-in-cheek. A calorie is that amount of heat required to raise one lb of water by one degree F.

So in that respect a calorie is still a calorie, and always will be

How your body absorbs different nutrients and with what efficiency it does so is another matter.

Actually a Calorie is the amount of energy required to raise one Kilogram of water on degree C. It's metric you know.

OOPS! I gave the definition of a BTU. Sorry! The statement still holds, regardless of the units used.