Why Calories count (where weight change is concerned).

I have to add the words "where weight change is concerned", as calories have little to do with body composition or general health (unless somebody becomes morbidly obese).

From https://docs.google.com/file/d/0Bz4TDaehOqMKSXZHUUVxWnl5VTQ/edit?usp=sharing

Arguments used by Calorie Denialists include:-

1) Calories don't count because the human body isn't a Bomb Calorimeter and treats different macronutrients differently.
 
100g of liquid paraffin burns in a Bomb Calorimeter, yielding 900kcals. In a human, it passes through completely undigested. Ah-ha!, I hear you saying. This proves that the Energy Balance Equation is invalid. Uh, nope!

Calories in = Calories entering mouth - Calories exiting anus

As 100% of liquid paraffin calories entering the mouth exit the anus, Calories in = 0

This is why Sam Feltham's "Smash the Fat" "experiment" is nonsense. A high percentage of the large amount of raw almonds he ate would have exited his anus incompletely chewed, undigested & unabsorbed.

See the picture above? In the late 1800's, W.O. Atwater established Atwater Factors (3.75kcals/g for digestible Carbohydrates, 4kcals/g for Proteins, 5kcals/g for Ketones, 7kcals/g for Alcohols & 9kcals/g for Fats*) using Human Calorimeters, not Bomb Calorimeters. Atwater Factors are pretty accurate.

*Fats containing different fatty acids have slightly different kcals/g. Fats containing long-chain fatty acids are 9kcals/g. Fats containing medium-chain fatty acids e.g. coconut oil are ~8kcals/g.

For more information, see Calories ...


2) Calories don't count because Dietary Efficiency varies for different macronutrients.

Uh, nope! The Heat Power generated by the body is regulated by a NFB loop involving the Hypothalamus, Pituitary, Thyroid Axis, also Uncoupling Proteins (UCP's), also shivering, so as to maintain a body temperature of 37°C ±3°C. If this wasn't the case, different amounts & types of foods (also, changes in ambient temperature & clothing) would cause large variations in body temperature resulting in death, as the enzymes in our bodies function correctly over a limited range of temperatures.

Heat Power generated by the body (W) = Temperature difference between the body & ambient (°C) divided by Thermal resistance between the body & ambient (°C/W)

∴ Dietary Efficiency is irrelevant.