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Ketoadaptation

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''"When first thrown wholly upon a diet of reindeer meat, it seems inadequate to properly nourish the system and there is an apparent weakness and inability to perform severe exertive, fatiguing journeys. But this soon passes away in the course of two to three weeks."<ref name="Speth2010"/>''
This was written during a 3000-mile Artic trek in 1879-80.
{{Skeleton}}=Achieving Ketoadaptation=* Adaptation typically takes a couple of weeks, but four weeks might be required for all adaptations.* An initial 24 hour fast may help, and is recommended for children starting [[Ketogenic Diets for Epilepsy| the Ketogenic Diet for Epilepsy]]. * Take the [[Ketogenic Diet Supplements]]. In the early stages is particularly important to keep water and salt intakes high, and broth is often recommended.* Failure to keep [[Net Carbohydrates]] and [[Protein]] intakes low enough will prevent Ketoadaptation. * [[Measuring Ketones]] is critical to make sure your diet is achieving Ketosis. * Expect to feel weak and [[Glycogen]] depleted during Ketoadaptation. Impaired mental functioning during Ketoadaptation is likely to be worse than a typical low fat diet.
=Adaptations and Timeframe=
* The scientific evidence around ketoadapation Ketoadaptation is limited as most studies use obese individuals that are undergoing a prolonged fastrather than a [[Ketogenic Diet]].* Ketoadaptation generally takes a minimum of two weeks, but some aspects may take longer. There is an initial phase of a few days that involves weight loss, mostly from Glycogen/water with some muscle loss, but little fat reduction.* Ketoadaptation generally requires a reduction in the availability of glucose. This is from primarily due to a reduction in net carbohydrate the [[Net Carbohydrate]] intake, but because the body will convert protein to glucose, the intake of protein must also be controlled.* Ketoadaptation generally takes a minimum of two weeks, but some aspects may take longer. * There is a reduction in [[Glycogen]], both [[Muscle]] [[Glycogen]] and liver glycogen. This takes a few days depending on exercise levels and is associated with weight loss as Glycogen is stored with water.* The levels of blood [[Ketones]] riseand the time between glucose dropping and ketones rising might contribute to the Ketoadaptation period. This rise in Ketone levels is probably due to improved reabsorption by the kidneys and reduced usage by muscles<ref name="Robinson-1980"/>.
* The ratio of Insulin to glucagon changes, with insulin levels falling. This may be a mechanism that triggers the generation of ketones, but in some situations ketones can be produced even with elevated insulin.
* Blood uric acid levels initially rise, before falling to baseline levels after 4-6 weeks. This can cause gout in susceptible individuals.
* The ratio between the [[Ketones]] AcAc and BOHB appears to change with adaptation.* During ketoadaptation Ketoadaptation the kidneys conserve ketones by reabsorption. ** Studies show that urine ketone excretion generally peaks after 4-8 days of fasting, and then diminishes<ref name="Sapir-1975"/>. (Renal conservation of ketone bodies during starvation)
** In fasted obese patients the rate of ketones (AcAc & BOHB) reabsorption increases 5x after 3 days and a further 2-3x increase from day 3 to days 10-24.
** The reduction in ketone excretion may be linked to the [[Protein]] sparing effect of the ketogenic diet.
** Because most studies of ketone reabsorption by the kidneys use fasting subjects it is unclear if the increased reabsorption is due to a change that occurs over time or due to the increased levels of blood ketones that naturally rise with prolonged fasting.
* Changes in protein metabolism and nitrogen conservation appear to occur within the first few days. For the first few days protein (muscle mass) is lost, but then stabilizes. Muscle mass can be maintained on a remarkably low protein intake when on the [[Ketogenic Diet]].* Changes There are changes in ketone blood/brain barrier.** The , and while the brain will use ketones if they are available, regardless of the level of glucose in ability to transport the ketones from the bloodinto the brain may improve over time.* Ketoadaptation can involve greater impaired memory functioning than subjects on a typical fat diet<ref name="D'Anci-2009"/>. Ketoadaptation can produce increased confusion, though this is slightly less than subjects undergoing a typical low fat diet<ref name="D'Anci-2009"/>.* The fuel usage of muscles changes with ketoadaptationKetoadaptation. ** In sedentary obese individuals on a 24 day fast the forearm muscles reduced the uptake of glucose, increased the intake of ketones (both AcAc and BOHB), and increased the intake of fatty acids<ref name="Owen-1971"/>. (Human forearm metabolism during progressive starvation.)
** Some, but not all, studies have shown that muscles will produce Ketones from free fatty acids.
=Loss of Adaptation=
How There are no indications of how long does it take takes to lose the adaptations?=See Also=Ketoadaptation.
{{KetoSeeAlso}}
=References=
<references>
<ref name="Robinson-1980"> AM. Robinson, DH. Williamson, Physiological roles of ketone bodies as substrates and signals in mammalian tissues., Physiol Rev, volume 60, issue 1, pages 143-87, Jan 1980, PMID [http://www.ncbi.nlm.nih.gov/pubmed/6986618 6986618]</ref>
<ref name="Speth2010">John D. Speth, The Paleoanthropology and Archaeology of Big-Game Hunting: Protein, Fat, or Politics?, date 8 September 2010, publisher Springer, isbn 978-1-4419-6733-6, pages 84–</ref>
<ref name="Sapir-1975">DG. Sapir, OE. Owen, Renal conservation of ketone bodies during starvation., Metabolism, volume 24, issue 1, pages 23-33, Jan 1975, PMID [http://www.ncbi.nlm.nih.gov/pubmed/234169 234169]</ref>
<ref name="Owen-1971">OE. Owen, GA. Reichard, Human forearm metabolism during progressive starvation., J Clin Invest, volume 50, issue 7, pages 1536-45, Jul 1971, doi [http://dx.doi.org/10.1172/JCI106639 10.1172/JCI106639], PMID [http://www.ncbi.nlm.nih.gov/pubmed/5090067 5090067]</ref>
<ref name="D'Anci-2009">KE. D'Anci, KL. Watts, RB. Kanarek, HA. Taylor, Low-carbohydrate weight-loss diets. Effects on cognition and mood., Appetite, volume 52, issue 1, pages 96-103, Feb 2009, doi [http://dx.doi.org/10.1016/j.appet.2008.08.009 10.1016/j.appet.2008.08.009], PMID [http://www.ncbi.nlm.nih.gov/pubmed/18804129 18804129]</ref>
</references>
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