RE: Calories Lost During Digestion

[Guest guest]

From Fienman's recent paper:

Review

" A calorie is a calorie " violates the second law of thermodynamics

D Feinman1 and Eugene J Fine1, 2

1Department of Biochemistry, State University of New York Downstate Medical

Center, Brooklyn, NY 11203 USA

2Department of Nuclear Medicine, i Medical Center, Bronx, NY 10461 USA

Nutrition Journal 2004, 3:9 doi:10.1186/1475-2891-3-9

The electronic version of this article is the complete one and can be found

online at:

http://www.nutritionj.com/content/3/1/9

Received 21 April 2004

Accepted 28 July 2004

Published 28 July 2004

" Efficiency and thermogenesis:

In nutrition, one component of inefficiency is measured in thermogenesis

(thermic effect of feeding), or the heat generated in processing food. There

is a large literature on this subject and the general conclusion, as

summarized in a recent review by Jéquier [15], is that thermic effects of

nutrients is approximately 2–3 % for lipids, 6–8 % for carbohydrates, and

25–30% for proteins. It is interesting that this data itself might be enough

to explain metabolic advantage. Here we took the average of Jéquier's values

(2.5, 7 and 27.5 % for fat, CHO and protein) and calculated the effective

energy yield for a 2000 kcal diet. If we assume a diet composition of

CHO:fat: protein of 55:30:15, within the range of commonly recommended

diets, the calculated effective yield is 1848 kcal. We now consider the

effect of reducing carbohydrate progressively and substituting the calories

removed equally between fat and protein. Figure 2 shows that the wasted

calories due to thermogenesis increase as carbohydrate is reduced and reach

100 kcal at 21 % carbohydrate. This value of 100 kcal is recommended by

several professionals as the goal for daily weight reduction (e.g. [16]).

Notably, at 8 % CHO, the value for the early phase of the Atkins [17], South

Beach [18] or Protein Power diets [19], 140 kcalories are lost as heat. Now,

there will be metabolic accommodations and one can't predict that the ratios

will stay the same over a long term diet, but the calculations show that the

possibility of metabolic advantage should not come as a surprise. "

>From: " loganruns73 " <loganruns73@...>

>Reply-

>

>Subject: [ ] Calories Lost During Digestion

>Date: Sat, 28 Aug 2004 06:47:20 -0000

>

>I read somewhere earlier that approximately 25% of calories is lost

>during digestion of protein, 15% for carbohydrates and 0% for fat.

>

>Does anyone know of any scientific proof for this claim?

>

>Logan

>

>

[Guest guest]

I think those are maybe optimistic. Data on bovine is more like 50% for pro and 50% for fat, but it varies a lot according to feeds. If you look at the BMR for me is say 1700 add 200 for routine motion. 200/1900 is 10.5 % efficient. If the digestion transfer function is 50%, the system eff is maybe 21%.

If you look at the actual work (physics) in walking 3 miles on flat ground is 50 kcals (150 # person ), yet 300 kcals is used. That's about 16 %. So including the 3 miles, overall efficiency is 23% (500/2200).

So I suspect the transfer function for digestion is around 50%.

But who cares? - It going to vary with the individual, the age, the physical condition. There has to be some precise info but I didn't find it yet.

Just my take.

Regards.

----- Original Message -----

From: loganruns73

Sent: Saturday, August 28, 2004 1:47 AM

Subject: [ ] Calories Lost During Digestion

I read somewhere earlier that approximately 25% of calories is lost during digestion of protein, 15% for carbohydrates and 0% for fat. Does anyone know of any scientific proof for this claim?Logan

[Guest guest]

" In weight loss diets, of course, inefficiency is desirable and is

tied to hormonal levels and enzyme activities. "

In a CR diet, is efficiency or inefficiency desirable? Anyone?

Logan

> From Fienman's recent paper:

>

> Review

>

> " A calorie is a calorie " violates the second law of thermodynamics

> D Feinman1 and Eugene J Fine

[Guest guest]

Hi Logan:

Logically, if the principal objective is weight loss then

inefficiency is desirable.

But in caloric restriction we are trying to use/process many fewer

calories. So inefficiency would be undesirable, I would think.

Rodney.

> > From Fienman's recent paper:

> >

> > Review

> >

> > " A calorie is a calorie " violates the second law of thermodynamics

> > D Feinman1 and Eugene J Fine

[Guest guest]

I'd say efficient, because I want to burn the least calories for a given weight, ergo ingest the least calories. If in addition, I can run at a cooler temperature and burn a little less, so much the better.

If we're talking CR. To lose weight drop that more calories.

Now I've wondered about efficiency in exercise, because aerobic is a lot more efficient. It has different byproducts though.

As far as thermodynamics is concerned the whole "laws of physics" are violated when you try to analyze actual work, etc. If you hold a 5# weight straight out for an hour you do no work, but you expend a lot of "biological" energy. When I started trying to quantify gym exercise with actual ft-lbs of work, I got a factor of about 5:1 indicating a 20% efficiency. The gym machines apparently assume the calories ingested to do that amount of work not the actual work done in the exercise. To prove that if you can do 20 flights of stairs on a stair climber, try walking up 20 flights of real stairs.

So yes 300 kcal is not 300 kcals, necessarily. 300 kcals of real work is a LOT of work.

Regards.

----- Original Message -----

From: loganruns73

Sent: Monday, August 30, 2004 3:02 AM

Subject: [ ] Re: Calories Lost During Digestion

"In weight loss diets, of course, inefficiency is desirable and is tied to hormonal levels and enzyme activities."In a CR diet, is efficiency or inefficiency desirable? Anyone?Logan> From Fienman's recent paper:> > Review> > "A calorie is a calorie" violates the second law of thermodynamics> D Feinman1 and Eugene J Fine