Nutrient Fates after Absorption

Random Bump

This held the top spot in terms of readership here at the Asylum for quite some time.  Always worthy of a bump.

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Original post:  7/15/10

Nutrient effects: post-absorptive interactions BY ERIC JEQUIER   (1995)

After a meal, the metabolic fuel selection at the whole-body level depends on the plasma concentrations of nutrients such as glucose, non-esterified fatty acids (NEFA) , amino acids, and on hormonal responses. Over the last 10 years, there has been great interest in studying the metabolic effects following the ingestion or the intravenous (i.v.) infusion of the three macronutrients, carbohydrate (CHO), fat, and protein (or amino acids for i.v. infusion). The aim of the present brief review  {I'm thinking it's not so brief!}  is to summarize the main mechanisms which determine the post-absorptive interactions between the nutrients.

This is an older paper, but still recent enough to provide some good info on the basics.  I'm going to do something a bit different with this one and I otherwise would be quoting huge chunks.  So I'll do bullet point summaries with select summary quotes from the paper in italics.

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Heat, Entropy & Thermogenesis

A summary post of ideas here, that I've likely stated elsewhere on the blog but wanted to gather in one place.  

Last week on Facebook, to the detriment of his credentials and credibility, Jason Boehm posted and deleted a post about calories and the Second Law of Thermo.  I queried what it had to do with the original point which was more of a 500 cals spinach vs. 500 cals Coke type nonsense, so he did address that in a second FB post that stands (minus lots of relevant input from people he deleted, labeled hateful and pretty much had a kitten over ... nobody called him a moron BTW, that's a clever tactic of those that can't hold up their end of an intellectual debate on the science ... can't leave the self-incriminating evidence).   But I digress.

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A Fein(man), Fine Mess of Thermodynamics

I was truly baffled beyond all bafflement (is that a word?) that Feinman & Fine wrote "A calorie is a calorie" violates the second law of thermodynamics, let alone that it passed the peer review process to be published in any reputable journal.  In the abstract they write:

Here, we propose that a misunderstanding of the second law accounts for the controversy about the role of macronutrient effect on weight loss and we review some aspects of elementary thermodynamics.

Here I propose that it is their apparent misunderstanding of thermodynamics, as put forth in this "study", that accounts for most of the gimmickry surrounding low carb diets in the community.  In the section entitled "Thermodynamics", they write:

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Cold Adaptation, BAT & Thermogenesis

Lerner posted a link to this study in comments on another post:  Cold-Activated Brown Adipose Tissue in Healthy Men.  A small part of the study where they looked at BAT activity for the three subjects with the most BAT under neutral thermal conditions caught my eye, and I think this is central to some of the confusion Kaptain Konfusion has introduced into this whole discussion.  They tested all subjects lying on their backs in a chamber, first for one hour in thermoneutral temp, next for 2 hours at 17C.  For three subjects they retested in thermoneutral temps for the entire time.  

There was no detectable brown-adipose-tissue activity in the three subjects who were retested under thermoneutral conditions. Brown-adipose-tissue activity was recorded in Subject 2 at 856.5 kBq during exposure to cold and 0 kBq in thermoneutral conditions, in Subject 3 at 587.2 kBq during cold exposure and 0 kBq in thermoneutral conditions, and in Subject 4 at 250.0 kBq during cold exposure and 0 kBq thermoneutral conditions.

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Some thoughts on cold exposure

Richard Nickoley/Free the Animal has posted a follow-up post entitled Cold Therapy and Adaptation and Ray Cronise.  Although he comments a few times, this comment addresses Ray's thoughts on it all.  So far I see no need for a warning label on this one ;-)  In any case, Ray presents some excellent information on the topic and I urge my readers to go take a look before diving into the icy water and trying to work up to hours on end in same.  For my part, after reading Ray, I think I may well get an inflatable pool and some pool dumbells and such and put it up in the back yard to exercise in this summer.  There's a town pool here, but if I have to drive somewhere I know compliance suffers, and although I have access to facilities where I work, no student gets to see me in a swimsuit!!

I admittedly don't know much about Ray as, in all honesty, I've only recently heard of him and Wim Hof what with all the recent buzz.  But he sounds knowledgeable and measured.  He has also apparently done extensive self-experimentation with appropriate equipment.  For example he seems to have looked at his body's metabolic rate response to various durations, etc. of cold exposure.  For all the recent hoopla over Kruse's TEDx talk, surgery and MRSA *epic* biohack, we learn from comments (if Lerner could save me the time to link again in comments that'd be great) that he didn't do the usual hormonal panels, etc., and he's not doing the metabolic rate measurements, etc.  We've apparently gotten all the documentation/proof we're ever going to get on that front ... Jack has moved on to using CT to treat patients and made some videos there.  

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