Alot of people i know who are trying to lose weight say things like ‘i gained 2 lbs yesterday’, even though logically gaining 2 lbs requires eating about 7000-8000 calories more than you take in. So that got me thinking about triglycerides and i have a few questions.
Why does 1 pound of fat = 3500 calories in popular culture if 1lb = 454 grams and 1g fat = 9 calories? Shouldn’t it be 4086 calories per pound or does the glycerol in the triglyceride, which im assuming is counted in the weight of fat but cannot be used for energy, skew the weight of bodyfat slightly enough so that only 3500 calories can be obtained from a pound? The Glycerol seems to have the chemical formula C6H6O6, which, going by g/mol weight would make it as heavy as 7.7 H-C-H’s in a triglyceride molecule. Assuming that this is the case, then woudl a normal triglyceride molecule have about 0.856% weight by H-C-H and 0.144% weight by glycerol? If so then i assume there would be about 15 H-C-H’s per chain in a triglyceride (45 total) which leads to the next question.
Is bodyfat stored in long chain or medium chain triglycerides? What is the chemical formula of a typical bodyfat triglyceride and how many H-C-H’s are there in one? I cannot find how many H-C-H’s there are in a typical triglyceride chain online, so for all i know it could be 10, it could be 800.
My copy of Lehninger is in my office, so I can’t address your math, but I can tell you that glycerol is a 3-carbon molecule with the molecular formula of C3H8O3. However, Glycerol is only one component of triglycerides, which result from the condensation of glycerol with three (“tri”-get it?) molecules of the fatty acid of your choice (the majority averaging about 16/18 carbons in length), giving a typical triglycerol a molecular weight of 854-938 daltons.
The simple answer to 1) from Jane Brody’s Nutrition Book:
The amount of water also tends to vary with age, with newborns having as much as 60% water and the elderly less than 25%.
The answer to 2) is much more complicated, and can’t be answered completely for any individual. True, about 95% of body fat is triglycerides, but that group has to be broken down by whether they are composed of saturated, unsaturated, or polyunsaturated fatty acids. And that appears to depend heavily on diet. According to an old textbook I kept, Nutrition in Clinical Care, by Howard and Bebold (1978):
The text doesn’t say what a breakdown of these might be for an average human.
Did it ever occur to you that maybe adipose tissue didn’t contain very much water? I’ll refrain from the personal insults.
“Roughly two thirds of the vertebrate body consists of water. The exact figure varies a great deal, particularly as a result of variations in fat content. Adipose tissue contains only some 10%, and a very fat individual, who may have half or mor of the body weight as fat, therefore has a low overall water content.”
Schmidt-Nielsen, Knut. 1997. Animal Physiology: Adaptation and Environment. 5th ed: Cambridge University Press. pp.93-94
only 10 percent ? that is almost exactly how much it takes to explain the discrepancy in the OP’s question. coincidence ?
wesley clark - okay you win. i did not see the guy mentioning water and protein. when i saw all those friggin structural formulas for fats i knew the thread is headed in wrong direction.