From: eepee@polaris.utu.fi (Esa-Pekka P{lvim{ki)
Subject: Re: Won't have Sex with a Fat Guy/Successful weight loss
Organization: University of Turku, Finland
Date: Tue, 10 Nov 92 12:47:22 GMT

In article <1992Nov6.141254.23870@magnus.acs.ohio-state.edu> jnielsen@magnus.acs.ohio-state.edu (John F Nielsen) writes:
>In article <1992Nov6.002701.23770@polaris.utu.fi> eepee@polaris.utu.fi (Esa-Pekka P{lvim{ki) writes:
>>>|> >Because of this, one cannot just stop eating or go on a very low
>>>|> >calorie diet. The person won't lose fat, they'll lose muscle mass
>>>|> >since it's protein is the only other source of glucose.
>>(I wrote:)
>>Wrong. The body will utilize fat first, proteins will be used in a much
>>later stage. Excercise; during long-lasting workout, the only source of
>>energy is fat. 
>
>Long distance runners actually experience a small drop in muscle mass
>but a much larger corresponding drop in fat.
>Check your info, before you call someone wrong. 

Don't have to check it. The first statement is still wrong, wrong, wrong.
It says: "the person won't lose fat". Wrong. He/She will. "Protein is the 
only other source of glucose" Wrong. Glycogen. Ketoacids. Fatty acids. Pyruvate
The whole statement is wrong in principle, because muscles don't primarily
use glucose for energy (except in anaerobic workout - anaerobic glycolysis) but
free fatty acids.

OK, maybe I exaggerated a bit by saying "the only
source", I'll correct myself: during long-lasting workout, muscles 
use fatty acids as the main source of energy, not proteins.

>The nervous system
>needs the 3-Carbon chains from glucose. Fat only provides 2-C
>chains(under real extreme circumstances fat can be used via a
>mechanism called ketosis). If you are not eating enough to feed your
>nervous system, the body will use protein(which also provides 3-C
>chains) not fat.

Mmm, detail. Well, this is why one should get approximately 150 g of carbo-
hydrates each day, considering total turnover (about 250g) and storages
(glycogen, about 450 g). About 75% of glucose deficiency is taken care of
by glycogenolysis, and about 25% of it is handled by gluconeogenesis OF
WHICH ketoacids, fatty acids, amino acids (from proteins) etc. are a part
of. So, let the CNS (central nervous system) use the glucose, 
let the muscles use the fatty acids, and accept the fact that
SOME protein will be lost on a diet, excercise a lot, and you're on your
way to the only succesful diet there is: greater energy expenditure than
intake.

Oh, and there's another thing to keep in mind as well, apart from this and 
the carbon chain numbers in glucose, and that's the fact that these
nutrients don't get to mess around inside the body any way they want to -
there are certain hormones to control them; insulin, glucagon to name a
couple. These also contribute to the fact that while on diet, it might
be good to pay attention to how often and how much to eat, not only how much
total to eat during the day...oh, and the use of glucose by the CNS is 
generally independent of insulin, oh, except e.g. for some appetite-regulating
nuclei of the hypothalamus.....

This is all to say it's a bit more complicated than just the carbon chains.

>This is basic nutrition. If you are still questioning me, I will go
>quote from a recent Nutrition Textbook.

This is basic physiology. If I got something wrong, please do correct me -
maybe I'll have to go back to the books..

/ep