Concept2 Forum

I just sent this to the UK forum and decided copy it and post here as well:

One item always seems to be overlooked in discussions of nutrition and that is "calories eliminated." I am sure that many people would be too squeamish to bring this up, but, from what I have seen of this forum (the UK, that is), it should certainly not be a problem here. In the case of ruminants, it is obvious that there are plenty of calories left in their droppings since they have been used as fuels in many parts of the world and still are in some places. Of course a good part of that is undigested cellulose, but they have the capability to metabolize cellulose (or have the microorganisms that do), so there must be some inefficiency there. Since humans are unable to metabolize cellulose, the usual fiber listed in foods is just going to be passed unchanged, but I don't think that fiber is included as part of the calorie content of human foods. I tried a rough search to try to find any reports of just how much non-cellulose fuel is left in human feces, but with no avail. I do remember that over forty years ago,I read a news item that NASA had some chemists working on the fuel content of human feces to see if it would be practical to mix it with an oxidant as a supplemental rocket fuel. The implication was that there was plenty of fuel still left in it and it seems unlikely to me that very much of it could be accounted for by materials like cellulose that cannot be metabolized. To me, that says that human metabolism is not all that efficient and that calories excreted should be included in the equation that calories ingested be equal to calories burned to maintain constant weight.

The subject of differences in efficiency of metabolism frequently comes up in these discussions. I have never seen anything really definitive on this, but I am convinced that it is real.

Bob S.

Bob,
That is a very interesting thought.
I thought the the energy value of foods was done with a bomb calorimeter (or similar device), in which case fiber would also be included in the Calorie count. I hadn't, however, thought about the fact that not all the food we ingest is completely metabolized. I would agree, therefore, that differences in metabolism would also be a factor in weight loss/gain.
I know for me that I can eat more Calories than most people that I personally know, even ones who are also physically active and a similar age, without gaining weight. That is even though I am relatively small. I won't ever eat diet foods, and like to eat lots of ice cream and fried foods, along with other, 'healthier' , foods. I am pretty sure I have a higher metabolic rate than normal, but I also have Celiac disease, so don't digest foods as well as normal. That probably leads me to have more Calories pass on through .

David

Bob S. wrote:To me, that says that human metabolism is not all that efficient and that calories excreted should be included in the equation that calories ingested be equal to calories burned to maintain constant weight.
Bob S.

So the formula is calories in minus calories out. Lets assume that the efficiency for human consumption is 100% of sugar, fat and protein, and 0% for fiber - we are talking about a nominal amount of calories. So just use the formula calories in minus calories out minus 10% of calories in to make certain you cover it and see where that leaves you. If you are on a one pound per week program, then you are burning 3500 more calories than you are taking in. I think the differential will not show up if you are true to that formula.

N