On a side note - Hoodoo, if you have any articles or links to good research re NST in humans, I'd love to see em as it has applications within my sphere too.
NST in humans
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I sent Cody an email and a few days later he left a message for me on my answering machine. Said he'd call back but I haven't heard from him.
NST is well known among neonates and people who are cold acclimatized. Not sure about acclimation though in humans. Most of the research on that is pretty old. Most of the work on NST has been done on rats, mice, hamsters, and voles. Is there something specific you are intersted in? I have tons of papers on NST.
NST is well known among neonates and people who are cold acclimatized. Not sure about acclimation though in humans. Most of the research on that is pretty old. Most of the work on NST has been done on rats, mice, hamsters, and voles. Is there something specific you are intersted in? I have tons of papers on NST.
Interesting, I shall have to read it.
As part of my degree, we had lectures on the effects of exercising in the heat and cold. As a broad overall rule, we were taught that you don't acclimatize to the the cold but you do to heat.
Having just had a look over some journals for NST, I can see that the lectures were telling us lies!
I think it's probably the extent of adaptation that occurs, that they mean.
Hoodoo,
So do you think that the idea of eating more meat is to compensate for the body changing from glycogen metabolism to increasing amounts of fat metabolism? My nutrition lecturer was the consultant to a chap who went to one of the poles last year (youngest guy?) and he told us the diet he had prescribed. Basically, it involved lots of fat!
As part of my degree, we had lectures on the effects of exercising in the heat and cold. As a broad overall rule, we were taught that you don't acclimatize to the the cold but you do to heat.
Having just had a look over some journals for NST, I can see that the lectures were telling us lies!
I think it's probably the extent of adaptation that occurs, that they mean.Hoodoo,
So do you think that the idea of eating more meat is to compensate for the body changing from glycogen metabolism to increasing amounts of fat metabolism? My nutrition lecturer was the consultant to a chap who went to one of the poles last year (youngest guy?) and he told us the diet he had prescribed. Basically, it involved lots of fat!
Stew said:
The advantage fat has, especially when toting your own food, is its energy density - you get more calories out of a pound of butter than a pound of brocolli.
Main disadvantage is that it doesn't liberate its energy fast enough to be used as the primary fuel for high intensity activity.
Yep, that's right.
Just looking at some research on it now. Back in 1980, they thought that increased catecholamine release in the cold was causing greater levels of fat burning, but I've just seen some from '91 that contends that thought. Although they were finding higher catecholamines, there were low levels of glycerol (indicator of fat use) and concluded that fat use in the cold was the same as in "normal" conditions.
Where's Hoodoo when you need him... :-?
Just looking at some research on it now. Back in 1980, they thought that increased catecholamine release in the cold was causing greater levels of fat burning, but I've just seen some from '91 that contends that thought. Although they were finding higher catecholamines, there were low levels of glycerol (indicator of fat use) and concluded that fat use in the cold was the same as in "normal" conditions.
Where's Hoodoo when you need him... :-?
Some interesting thoughts guys. To be honest, I haven't delved into the human literature on this in a long time. I used to know the NST literature cold until I switched from mammals to insects in my research. So I'm out of the loop on some of the recent research on diet and cold adaptation. But I do believe there's more to it than what we see in terms of traditional biochemical pathways. Lundin touched on this when he discussed Diet Induced Thermogenesis although the mechanism he described for it was way off base. Evidently he got his info from a book on winter ecology by Tim Halfpenny. I need to look that book up.
Anyway, to make a long story short, we know precious little about the affect of DIT on cold acclimation. To put it in a nutshell, DIT results from consuming an unbalanced diet. So if you consume a high fat diet or a high protein diet or a high carb diet, or a low fat diet or a low protein diet or a low carb diet etc, you will utilized the diet with less efficiency than a "balanced" diet. In fact, this is how the term "balanced" diet was originally defined, by the amount of thermal energy it produced (i.e., "wasted" energy).
There is certainly a lot of anecdotal evidence to indicated that a high-protein diet will keep you warmer in the cold. A good book on this topic is Kabloona, about a guy who lived with some traditonal Inuit. I can dig up more info on this when I get home.
Anyway, as for DIT, I'm going to refer you to a paper written by an incredibly brilliant scientist:
http://www4.gvsu.edu/triert/research1/DIT03.pdf
Anyway, to make a long story short, we know precious little about the affect of DIT on cold acclimation. To put it in a nutshell, DIT results from consuming an unbalanced diet. So if you consume a high fat diet or a high protein diet or a high carb diet, or a low fat diet or a low protein diet or a low carb diet etc, you will utilized the diet with less efficiency than a "balanced" diet. In fact, this is how the term "balanced" diet was originally defined, by the amount of thermal energy it produced (i.e., "wasted" energy).
There is certainly a lot of anecdotal evidence to indicated that a high-protein diet will keep you warmer in the cold. A good book on this topic is Kabloona, about a guy who lived with some traditonal Inuit. I can dig up more info on this when I get home.
Anyway, as for DIT, I'm going to refer you to a paper written by an incredibly brilliant scientist:
http://www4.gvsu.edu/triert/research1/DIT03.pdf
How about this?
Diet induced thermogenesis measured over 24h in a respiration chamber: effect of diet composition. (Only the abstract)
Diet induced thermogenesis measured over 24h in a respiration chamber: effect of diet composition. (Only the abstract)
Good link Stew. That's pretty typical of DIT studies. If you go WAY back, they used to call it Specific Dynamic Action, the nature of which was little understood, but the response was measured over a short time period, i.e., right after a meal. In SDA, it's long been known that a diet of pure protein has the highest SDA.
In the world of agriculture, they called it Heat Increment of Feeding and farmers wanted to feed their animals a diet with the lowest HIF to save money. In other words, they wanted to feed them a diet that was the most efficiently utilized and produced the smallest thermal increment.
In the world of agriculture, they called it Heat Increment of Feeding and farmers wanted to feed their animals a diet with the lowest HIF to save money. In other words, they wanted to feed them a diet that was the most efficiently utilized and produced the smallest thermal increment.
I split this off from the thread in the library formus.... thought it was getting a bit off topic so I put it here ;-)
Ed
Ed
Hoodoo said:
No, nothing specific, just a general "if you've got any interesting online articles, I'd like to read em" sort of thing. To explain, perhaps I'm comming from a point of interest when the mechanisms of thermoregulation go wrong or get disrupted in humans. I work in a trauma ICU, which specialises in head injuries, apart from obvious mechanisms of injury to the thermo-regulatory areas - the hypothalamus, we also see a lot of patients with cerebral oedema, some cases enough to cause loss of pupilary response and even tentorial herniation. In addition, the anaesthetic drugs (neuroleptics such as haloperidol) and gasses (halothane) we use, can disrupt propper thermoregulation. As well, we see numerous infections, which cause febrile convulsions - I've had to pack patients in ice before now.
Just generally interested really.
Well, the old dogma is that unless you were raised in the cold, your capacity for NST as an adult is minimal. That's why I found Cody's book so interesting, because he attempts to acclimate to the cold and stimulate his capacity for NST. My guess is that there is only a slight affect. The whole key to NST in mammals is having large depots of a tissue called brown fat. This fat is a lot different from white adipose tissue. It's main function is to burn energy (under the control of the hypothalmus). There is a lot of brown fat in newborns but how much is found in the adult human is a question of controversy (at least, the last time I looked into this). :-D
IIRC, Brown adipose in humans is usually found in the back and shoulders in children. Problem is (as you say), the depostis and distribution of brown/white adipose change as we mature out of infancy and the whole regulatory mechanism become more hypothalamic mediated. (it's a while since I've covered this stuff in any depth, so I may be off).
The reason for the greater amount of brown fat in children is to offset the thermal instability of having a much higher surface area to volume ratio than adults. As we get older, our SA:V ratio decreases (our body volume increases in comparison to our surface area), and we are less prone to swings in thermal control - we're more stable, so we dont need the brown fat and loose it in favour of the white stuff.
The reason for the greater amount of brown fat in children is to offset the thermal instability of having a much higher surface area to volume ratio than adults. As we get older, our SA:V ratio decreases (our body volume increases in comparison to our surface area), and we are less prone to swings in thermal control - we're more stable, so we dont need the brown fat and loose it in favour of the white stuff.
