|Nov10-10, 05:56 PM||#1|
How does a dietary intake of 100% animal fat mimic fasting?
I have read some things such as reports of the Stefansson Bellevue experiment, or his reports of the Eskimos, and a few references to the research of Pennington, Kekwick, Donaldson, MacKarness, and their having patients on a dietary intake of low carbohydrate or very low carbohydrate, moderate protein and high fat. These dietary regimes are for ongoing nutrition, or care for those who have allergies or need to lose weight.
With more research being done about ketogenic diets for those with cancer, epilepsy, Alzheimer's, and other serious illness, this brings new avenues of possibility. There are many on low-carb and Paleo forums who post reports of doing very well on ketogenic diets, in many variations.
I am interested to know if the rest and regeneration which fasting gives would be duplicated, for lack of a better word, by a diet of 100% fat, say 100% pastured beef suet, for something which has nutrients and a good Omega 3 to 6 ratio. Hydration with clean water, free of contaminants and additives.
Would the diet of animal fat supply the body with nutrients so that the unwanted aspects of fasting are avoided, while giving the body the specific benefits that fasting does?
I apologize, I do not know enough to ask more specific questions.
If there are those among you who are interested in such things, and wouldn't mind explaining this to a "lay person", I would appreciate whatever you'd be willing to post.
Thank you very much.
|Nov11-10, 11:55 AM||#2|
Your body needs carbohydrates, period. Despite what any "new age" diet "gurus" claim. Your brain and red blood cells can only use glucose (and ketone bodies under starved states, more on this in a minute).
Other cell types in your body prefer to use different nutrients for glycolysis, such as your intestinal epithelium which prefers to use glutamate for its carbon source.
If you eat a diet free of "carbs" your liver only sees the hormone glucagon (think "glucose is gone"). This sets off a cascade of events (namely through protein kinases) which turns off glycolysis in your liver and starts running gluconeogenesis. Why does your liver do this? Because as I pointed out above, your brain and RBCs need glucose.
Not all sources of carbon can be used to make glucose to feed your brain and RBCs. Most fats cannot be used to make glucose (the exception is odd carbon number chain fatty acids which produce a propionyl-CoA as the last step of beta-oxidation). Almost all amino acids are glucogenic (ie; they can be used to make glucose). Which in the case of a low carb diet isn't necessarily a good thing (if you're not eating enough protein) because that means your body will begin break down muscle (protein) to feed the brain and RBCs.
Your body has an inbuilt safety for this, under conditions of starvation your body assumes you require muscle (to hunt and gather more food) so your liver's main source for ATP during starvation comes from the oxidation of fatty acids (released from your fat stores, or from a "diet of 100% fat). The excess of acetyl-CoA under these conditions leads your body to produce ketone bodies, which the brain and RBCs can use for about 30-40% of their energy demands. This means (from your body's standpoint, less muscle degradation and longer buffer period where you can find food).
The problem with prolonging these conditions (asides from becoming hypoglycemic) is suffering from ketoacidosis, which affects your body in many negative ways (it turns out your body likes to maintain a certain homeostasis and doesn't take kindly to things like changing pH).
Omega 3 and Omega 6 fatty acids are just advertising gimmicks. What sounds safer to eat; omega 6 fatty acids or cis-9,12 linoleic acid? Probably the former, but they are one in the same.
Omega fatty acids are just unsaturated fats that your body can't synthesize (you cannot make the 9-12 or 9-12-15 split double bonds in the carbon back bones). So these are essential fatty acids (like you have essential amino acids) you need as precursors for more complex fats, which you mostly use for cell-cell signaling (like prostaglandins).
If you want to feel good and have a healthy diet don't spend money on new age guru books, learn about evolution (you know the unifying theory of biology; "nothing in biology makes sense except in light of evolution"--Including our diets). We evolved over the last few million years eating seasonal varied diets of complex plant carbohydrates, simple animal carbohydrates, lean meats and healthy animal fats. Spending your time emulating that, making sure you meet your essential nutrient (including vitamins) demands and staying physically active should lead to desirable outcomes, any genetic problems aside (and you save the 14.95 you would have spent on a book called "stuff my pockets and follow my ridiculous diet" to boot).
|Nov12-10, 05:33 PM||#3|
Bobze, thank you for taking the time to post.
My question is one of scientific interest.
I like to find out about things, and be able to answer specific questions, and ask questions of others, when subjects arise.
I asked the question on this forum, because I would like to know to know the chemistry involved.
|Nov12-10, 09:11 PM||#4|
How does a dietary intake of 100% animal fat mimic fasting?
|Nov15-10, 09:37 AM||#5|
Well there are lots of myths and misconceptions about carb and fat in the media and establishment.
Lets start with the common one that the body, esin needs carbs.
The body does not need dietary carbs, but will use them if supplied. If we dont eat enough glucose to fuel the brain, the liver can synthesis ketone molecules. Our bodies can manufacture all our glucose needs via gluconeogenesis, the process of converting protein into glucose. Also, some tissues which prefer carbohydrate metabolism to ketone metabolism, like our brain, will eventually convert to at least partial ketone metabolism.
And ketosis is very different from ketoacidosis, a commonly made mistake people use to portray low carb as a <shudder> <shudder? horrible thing.
Dietary ketosis is among the most maligned and misunderstood concepts in nutrition because it is often confused with ketoacidosis, which is a life-threatening condition most often associated with uncontrolled insulin-deficient Type 1 diabetes. In the Type 1 diabetic, the absence of insulin leads to a toxic build-up of blood glucose and an extreme break-down of fat and muscle tissue. This condition doesn't occur in individuals who have even a small amount of insulin, whether from natural production or artificially administered.
Dietary ketosis, however, is a natural adjustment to the body's reduced intake of carbohydrates as the body shifts its primary source of energy from carbohydrates to stored fat. The presence of insulin keeps ketone production in check so that a mild, beneficial ketosis is achieved. Blood glucose levels are stabilized within a normal range and there is no break-down of healthy muscle tissue.
The most sensitive tests of ketosis ("NMR" and "blood ketone level") show that everyone is in some degree of ketosis every day, particularly after not eating overnight and after exercising. Ketosis is the body's survival system. It is not an abnormality nor does it present any medical danger, except to a Type I insulin-dependent diabetic. The body functions naturally and effectively while in a state of dietary ketosis.
The danger of excess carbs, especially refined carbohydrates, is well known. Its no longer controversial or unproven. On the other threads, I have posted lots of evidence of the harm of carbs as well as the lack of evidence that saturated fats are bad.
|Nov15-10, 11:08 AM||#6|
*Slight fyi gluconeogenesis is not the process of converting protein into glucose. It is the process of making glucose from any available carbon source. Glycerol, lactate, propinyl-CoA etc.
Because the regulation of ketone bodies is not as regulated as other metabolic cycles. The production of "ketone molecules", is for better or worse, controlled by the amount of available acetyl-CoA available in the mitochondrial matrix. An abundance of AcCoA will lead to KB formation, whether it is poisoning your body or not.
AcCoA is the outcome of beta-oxidation of fats. So when your body is running B-oxidation, it naturally has an excess of AcCoA (important note here, CARBONS FROM AcCoA CANNOT BE USED FOR GLUCONEOGENESIS, the consequence of which means some substances, like lysine for instance, are ONLY ketogenic). In an evolutionary sense this makes "senses".
If the body is starving then you are burning only fat stores for energy. This also means blood glucose levels will be low (hypoglycemic) and the brain and RBCs energy demands maybe in peril. Making ketone bodies in this situation then would be beneficial.
The problem comes in disease states (extended starvation, anorexia, alcoholism, diabetes, or people who buy in too goofy diets) when KBs reach dangerous concentrations.
Edit to add: I suppose you could make the argument that insulin indirectly contributes to KB production (rather the lack of insulin), because of the increase in glucagon/insulin ratio, which further activates HSL, thus raising even more blood FFA levels.
Your blood glucose levels need to be maintained at about 90 mg%. Insulin only helps lower higher BGLs to this point. It does so by allowing cells such as muscle to take up glucose and by starting insulin-dependent cascades which result in the promotion of glycogen formation.
Glucoagon is responsible for bringing your BGLs up to this level when they are too low. Muscle DOES NOT HAVE GLUCAGON receptors, so with a increased glucagon/insulin ratio the muscle will not uptake blood glucose stores. While other organs, like the liver will respond through glucagon dependent cascades (namely through PkA) to start gluconeogenesis.
Your muscle glycogen stores run out very quickly (measured in the hours) and those metabolic end products (lactate) will be sent to the liver for gluconeogenesis. If you continue to not eat carbohydrates, the muscle will begin metabolize protein so that glucogenic amino acids can also be sent to the liver to raise and maintain blood glucose levels.
At about this point, the continued exposure of glucagon will activate hormone sensitive lipase, which causes fatty acid metabolism to start. The elevated blood level rise of fatty acids induce carnitine transport in the liver, where b-oxidation will result in increased AcCoA and as discussed above, will increase KB formation. The point of the KBs is to protect against muscle protein catabolism. And ketosis.
Continuing to not eat (or eat incorrectly) will result in even more fatty acid metabolism and even greater increases in KB formation and after extended periods of this ketoacidosis.
Reading a "popularize of science book" (by a physicist too no doubt) isn't an alternative to medical education nor seeking real medical advice.
|Nov15-10, 10:02 PM||#7|
As for the second part of your question. Fat and water are not the only things your body requires. Amongst the more important molecules your body requires are electrolytes, micronutrients and proteins. Electrolytes imbalances can cause illness/death in hours to days whereas micronutrient and protein deficiency typically takes much longer (months) and aren't typically lethal but can cause serious illness and/or lower quality of life (at best).
I've done everything from Straight/Cyclic/Targeted Ketogenic Diets, to Protein Sparing Modified Fasts, to Intermittent Fasting to Carb Cycling to just straight calorie deficits with balanced macronutrient profiles etc, High Carb/Low fat, High fat/Low Carb and many in between. Come to think of it, the only macronutrient I've never cut out was Protein which makes sense because I came from a bodybuilding backround.
There is so much crap out there that if a person is not well versed in fundamental science then its almost impossible to tell the pseudoscience from the real science (euscience?). I'll just share a tidbit with you that most 'health/diet gurus' never will. Every single one of the diets that you ever read about will work. Fad diets trick you into eating less while telling you that you can eat as much as you want. Losing weight is a simple matter of calories in versus calories out. You create a caloric deficit via a)eating less or b)moving more and you will lose weight. The same can be said of any fad diet that is not necessarily promoting weight loss, but just good health. The easy part is following the '4 Phase Plan' as spelled out by the all knowing [insert guru here]. The tough part is actually maintaining a regimen which is both sustainable and healthy in the long run. The tough part is developing a balanced lifestyle which includes being 'mostly' healthy while maintaining your sanity at the same time. I say mostly because I've yet to meet a person, who is sane, who can really maintain one of those paleo-starvation-what-have-you diets 100% of the time for years on end. Everything in life is good for you, the key is knowing where/when/how to maintain the appropriate balance of the good-bad.
General rule of thumb, if someone is telling you that their method is the best method for everybody, across the board and at the same time is trying to explain how everything everyone else is doing is bad and wrong and that you need to buy their 3 phase diet plan or whatever, run and hide. They don't know what the hell they are talking about or they know exactly what they are talking about but they really want to make some cash. With overweight and obesity rates sky rocketing in most developed nations, everybody is looking for that quick, easy, black and white type of answer. The problem is that nothing in reality is ever black and white. Reality, IMO, is pretty much all shades of gray.
|Nov16-10, 01:38 AM||#9|
bobze, i'd like to see some evidence that increased protein metabolism is bad for your kidneys. just because an increased BUN reading could indicate a kidney problem does not mean that increased excretion of urea is going to do damage.
in any case, if i were going to fast, i'd do a protein-sparing modified fast to control hunger and limit lean tissue losses. plus some fish oil for EPA/DHA and a multivitamin to limit nutritional deficiencies. it's no way to live, but then, neither is being obese.
|Nov16-10, 05:19 AM||#10|
There's plenty of evidence that high-protein diets are bad for people with some kind of preexisting kidney damage, even if it's mild, e.g.
The effect on healthy kidneys is more controversial. Studies usually focus on short-term measurable effects such as the decrease in filtration rate, and that is not seen in people who switch to a high-protein diet. On the other hand, you're not going to find short-term measurable effects on the lungs in someone who starts smoking, either. And then at some point after 20 or 30 years the body reaches the limit and things start to break down.
Back to kidneys, at least one study back in 1990 found that people from the top quartile by protein intake had double the risk of renal cancer compared to people from the bottom quartile. 2x is not much and this cancer is quite rare to begin with. But, on the other hand, this was long before Atkins became a fad, and quantities of protein consumed by modern low-carb dieters are probably unheard of by the standards of 1990. Could be a good idea to get into the dialysis business by the time early adopters of Atkins start getting into their 60's.
|Nov16-10, 06:05 AM||#11|
Damn, thats a long post
I dont see you actually refute anything I said.
First you (thankfully) move away from saying our body definitely needs carbs to agreeing that 40% of these carb needs can be met by ketones. You further agree that the remaining can be met by gluconeogenesis, although you quibble over whether all compounds are glucogeneic. I can live with you disagreeing over that. As long as we've busted the myth that the brain can function only on carbs and all those carbs have to come from diet. And we've busted that big time, thanks
And re: the cliched claim that "amino acid (protein) metabolism leads to increased BUN levels, which negatively affect both your kidneys and your liver", Evidence please.
You also agree that there is a difference between ketosis and ketoacidosis. Thank you. Most people who shudder at the word ketosis are misplacing their shuddering by understanding ketosis as ketoacidosis.
But you seem too think that ketoacidosis is some progressively worse form of ketosis, which is not entirely correct.
BTW here is a study that shows how "dangerous" ketosis actually is
Maybe all the metabolic processes that lead to ketone production in ketoacidosis are present in ketosis, yet ketosis will not lead to an acidotic condition.
Here's a lovely link that explains it well.
BTW not sure if you have read Dr. Bernstein. He has worked wonders in people with diabetes. With very low carb diets.
|Nov16-10, 06:24 AM||#12|
In fact fitness experts have been trying to bust this myth for decades. They regularly eat high protien diets.
Here's the abstract :
In fact our protien needs may have been underestimated. A 1994 study revealed the increased needs for the elderly.
|Nov16-10, 07:49 AM||#13|
What we really need is to look at the rates of chronic kidney disease and ESRD among the elderly (60+) and correlate them with (possibly self-reported) average lifetime protein consumption levels. We already know that a high-protein diet accelerates the progression from mild renal insufficiency to chronic kidney disease (link above) and from CKD to ESRD (http://ndt.oxfordjournals.org/conten.../1986.abstract). All we need is to connect the dots: even assuming that renal insufficiency is equally likely to occur among Atkins followers and carb eaters, the former group is far more likely to end up on dialysis. But I'm not aware of such study. And the myth of safety of high protein diets lives on.
|Nov16-10, 11:17 AM||#14|
Its not only BUN levels, but blood acidity in general. On most western diets we are slightly acidotic because of increased protein consumption. Your kidneys are built with an excess of nephrons, which in most cases mitigate this acidosis. But the general effect is to require your kidneys to work harder.
Increases in protein metabolism also lead to increases in ammonium excretion (through tubule lumen hydrogen ion loading), which is good because it reduces ammonia levels, but at the same time reduces concentration of final urine (not provisional, which remains isosmotic) and again requires more work on the kidney.
The problem with kidney disease (as apparent to anyone who's studied renal physiology) is the excessive GFR (glomular filtration rate), which glomular function doesn't take a "dive" until we've reached around 15% of our glomular function.
This is pretty basic medical renal physiology. For more information, I'd recommend Vander's Renal Physiology.
*Just a note, I'm not saying "protein diets" are "bad", just as I was not saying that "carb diets" are "bad". We're far to individual for that. I will say, what I said a while ago, that if you really want a healthy diet you should seek to emulate that diet we evolved to eat. Namely, complex plant carbs in variety, lean meats and simple animal carbs and healthy animal fats. As Yanick pointed out though, the discipline required to adhere to such "stone-age" diets, is too much for most American's (and Westerners) in general, who live by the American motto of miracle cure-all's and get rich quick schemes.
The reality in our modern setting is that hard work and discipline are required to maintain health, there is no free lunch.
|Nov16-10, 11:59 AM||#15|
. Of these only B-hydroxybuterate can be shipped around the body for a potential fuel source, where it is converted to acetoacetone then undergoes 1 round of B-oxidation to make 2 acetyl-CoAs. AcCoA is the ONLY ketone your body can use for energy production, which involves TCA cycle.
Secondly; I pointed out that your body can use ketone bodies to meet some of the brains energy demands in my first post. SOME being the operative word here, accounting for 30-40%. Aside from that, the brain MUST have glucose. Your brain cannot meet its total energy demand for energy through KBs. IT WILL DIE WITHOUT GLUCOSE.
The brain prefers glucose to all other energy sources, just as intestinal epithelium prefers to use Gln. Different tissues preferentially select carbon sources over others and removal of said sources leads to dysfunction of the tissue (and in some cases, such as the brain, to tissue failure).
Again, the most efficient way for the body to regulate blood glucose is through ingestion of glucose and storage as liver glycogen. If you disagree with this, please study glycogen storage diseases.
As Hamster pointed out, its evident in people with decreased glomular function that high protein diets in individuals in diseased states suffer more because of this. As to the effect on "healthy" people, the long term trends remain to be seen. Again, I'm not advocating "against" protein as you seem to suggest. The only one here that seems to advocating (in a rather uninformed manner) against a "culprit" macronutrient are these get rich quick dieters. The bottom line is, your body needs all macronutrients to maintain a healthy balance.
Again, if you want a healthy diet, try and emulate what we evolved to eat.
Elevated KBs isn't the "natural state" of the human body, it is an adaptation to decreased nutrition from starvation. KB levels don't rise to measurable amounts till around ~48h without proper nutritional needs.
I don't need a "blog-spot" to explain them to me. As I pointed out in my "about me" post, I am a medical student, I've studied them more in depth than is offered on the "blog-spot".
Even more important than "low carb diets" in type II'ers is low caloric diets.
Low calorie or low carb diets are NOT appropriate treatments for type I diabetics. Who have no basal insulin because of (most often) an autoimmune response against the pancreatic-beta cells. These people need insulin administered, and the different types of insulin (there are different biological half-life types, such as "long lasting insulin") and have to control their diets based on the peak-presence of insulin. However, with fast acting insulin and insulin-pumps becoming more prominent over the last 25 years, many of these people are free to lead a more "normal" life-style and diet. Though, since many of them tend to error on the side of hypoglycemia, it remains to be seen the long term effects of such a state and over the next couple of decades we'll undoubtedly see what affects this has, if any.
I'm not sure why you are on a hiatus against "carbs" other than being suckered by diet gurus. For the 3rd time in one day, if you want a healthy diet, emulate what we evolved to eat. Which certainly includes carbs. The problems Americans are faced with isn't the "evil" carb, its the excesses of macronutrients and calories in general, coupled with a relatively inactive life-style. We want a lot for little investment and unfortunately, health doesn't work that way.
|Nov16-10, 02:58 PM||#16|
but the protein myth of destroying your kidneys is just that. and what constitutes "high" protein depends on who is perpetuating the myth (promoting veganism say, versus attacking bodybuilding or paleo nutters). at this point, as you guys have pointed out, all we have is a bunch of speculation, save some things that happen in people abusing steroids that no doubt clouds the matter in the minds of docs that have formed a bias.
it would also be nice if the people that want to perpetuate the "protein is bad for your kidneys" myth would give a recommended upper limit, say in something like grams_protein/kilogram_bodyweight/day.
|Nov16-10, 08:11 PM||#17|
And most of the blogs I reference are written by doctors and experts in biochemistry. None of them are diet gurus. So even a well-intentioned medical student can learn something there
We evolved to eat a lot of meat. And a few berries and tubers.
There were no grains and no refined flour (or other refined carbs), sugar or HFCS for more than 90% of our evolutionary history. In fact, right upto the early 1900s, the common sense approach of weight loss was to avoid refined carbs and sugar. Its only after Keyes and a few others started spewing nonsense and the media gobbled it up that the tenets changed.
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