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* Blood levels of the [[Ketones| Ketone]] 3-hydroxybutyrate (BOHB), which indicates ketogenisis, were insignificant on the normal diet and elevated (1.28 mmol/L) on the [[Ketogenic Diet]].
* Muscle [[Glycogen]] levels where higher before the endurance test on the normal diet than on the [[Ketogenic Diet]] (143 and 53 respectively). Both tests had similar muscle glycogen levels after the endurance tests. It is interesting to see that muscle glycogen levels were replenished somewhat on the [[Ketogenic Diet]], even though the subjects continued normal training for the four weeks.
{| class="wikitable"
!
! Endurace-1
! VO2-2
! Change
! RQ-2
|-
| JP
| 3.20
| style="background-color: #FDC77D;" |-3%
| 0.65
|-
| IK
| 2.97
| style="background-color: #F8696B;" |-4%
| 0.75
|-
| MK
| 3.01
| style="background-color: #FFEB84;" |-3%
| 0.72
|-
| BK
| 3.97
| style="background-color: #B6D680;" |5%
| 0.72
|-
| WB
| 2.95
| style="background-color: #63BE7B;" |13%
| 0.74
|-
| Average
|
| 2%
|
|-
| Exclude WB
|
| -1%
|
|}
=Other studies=
There are a few other studies that are of interest, though they do not directly deal with exercise capacity and the Ketogenic Diet.
==Metabolic characteristics of keto-adapted ultra-endurance runners (FASTER)==
This study compares the characteristics of 20 elite endurance athletes, 10 of them having been on a long-term low carbohydrate diet<ref name="VolekFreidenreich2016"/>. The study is sometimes referred to by the backronym FASTER (Fat Adapted Substrate use in Trained Elite Runners.) The athletes on the low carbohydrate diet had higher levels of fat burning than their high carbohydrate comparisons, but did not seem to have any of the benefits that high fat burning would normally convey.
* The subjects were 20 elite ultrarunners or triathletes, finishing in the top 10%, some of them with course records, or national/international records. The athletes had broadly similar average characteristics.
* While the title of the study suggests that the athletes are on a [[Ketogenic Diet]], this does not appear to be the case. The low carbohydrate athletes had a resting [[Ketone Level]] of ~0.7 mmol/L, which I feel is borderline for Ketosis. Their diet indicates their [[Ketogenic Ratio]] was only 1:1, which is far too low for Ketosis and there is no information provided to indicate they are [[Ketoadaptation| Keto-adapted]].
* The study consists of two tests on consecutive days. The first day involved a [[VO2max|V̇O<sub>2</sub>max]] test and the second day a sub-maximal three-hour treadmill endurance run. The [[VO2max|V̇O<sub>2</sub>max]] test was after a 4 hour fast, and the endurance run was 90 minutes after a nutrient shake that was different for the high and low carbohydrate athletes. This difference in nutrient intake makes the results endurance run hard to interpret as it's impossible to know if the differences in results are due to the prior nutrition and training, or due to the different nutrient intake.
* The [[VO2max|V̇O<sub>2</sub>max]] test resulted in the low carbohydrate athletes had a 2.3x higher peak fat burning capability than the low carbohydrate athletes, both from an absolute and as a percentage of [[VO2max|V̇O<sub>2</sub>max]] where the peak fat burning occurred. This might suggest that athletes on a low carbohydrate diet adapt to being able to burn fat at a higher rate, or it might suggest that athletes with naturally higher fat burning capability are more likely to choose a low carb diet. (The overall [[VO2max|V̇O<sub>2</sub>max]] for the two groups was broadly similar with an average of 64.7 and 64.3, though both groups had a wide range of 55-76.)
* The endurance test was not to exhaustion and is more of a long training run. The intensity was 64% of [[VO2max|V̇O<sub>2</sub>max]], which a pace of about 100 seconds/mile slower than marathon pace.
* The biggest problem with interpreting the endurance test is that not only are the two group of athletes different, but the groups were given a shake with different nutrition 90 minutes before the test. It's impossible to know what variation between the groups results is due to prior training and what is due to the shake.
* The low carb shake consisted of heavy cream, olive oil, whey protein, walnut oil, and strawberries, which is seems to be a good choice of ingredients.
* The low carb shake is more problematic. It consisted of the heavy cream, olive oil, whey protein, walnut oil, and strawberries of the low carb shake, plus bananas and agave syrup. The high carb shake is nothing like the nutrition a reasonable athlete would consume. The carbohydrate in agave syrup is 67-90% [[Fructose]]<ref name="Figlewicz-2009"/><ref name="SRINIVASAN-1954"/>. This level of Fructose makes this a remarkably poor choice for athletes (or anyone else) as it is extremely slow to digest. The inability to digest the Fructose can be seen in the way the high carb athletes' blood glucose does not rise. It's impossible to know if this was simply a poor choice or if it constitutes an intentional bias intended to promote low carb nutrition.
* During the endurance test the low carb athletes burned more fat and less carbohydrate than the high carb athletes. Normally an increased fat burning capability is seen as a good thing in athletes as it helps preserves [[Glycogen]], which is typically a limiting factor in endurance events. However, both groups burned through similar amounts of Glycogen. The test was a fixed 3 hour run, so there's no way of knowing if either group would last longer before reaching voluntary exhaustion, but it seems likely that Glycogen levels would limit both groups equally. It also seems likely that a reasonable source of carbohydrate for the high carb group would have resulted in them using less Glycogen than the low carb group. (The study noted that the low carb athletes burned more Glycogen than the estimate for their total carbohydrate burn, which is rather strange.)
In summary, it's hard to interpret this study other than to conclude that a low carb diet does not impair [[VO2max|V̇O<sub>2</sub>max]].
==Non-Ketogenic Low Carbohydrate Diet (NKLCD) and Exercise==
A 1994 study looked at the effect of a low carbohydrate diet on cycling performance<ref name="Lambert-1994"/>. This study explicitly avoiding being ketogenic, providing calories from 67% fat, 7% carbohydrate and 25% protein, with a control condition of 70% carbohydrate. The exercise test protocol was rather unusual; a maximum strength test was followed by a [[High Intensity Interval Training| Wingate test]], then a high intensity (85% [[VO2max|V̇O<sub>2</sub>max]]) endurance test to exhaustion, a 20 minute rest, then a moderate intensity (50% [[VO2max|V̇O<sub>2</sub>max]]) endurance test to exhaustion. The high fat and high carbohydrate conditions were not statistically different except for the moderate intensity test where the low carbohydrate condition produced significantly better endurance (80 minutes rather than 43.) However, while the high intensity exhaustion test was not significantly different, the low carbohydrate condition was only 8.3 minutes rather than 12.5. This is not statistically significant, but it does suggest the high carbohydrate condition could have been far more tiring than the low carbohydrate condition. There have also been other studies showing that a rest period between exercise bouts can produce low blood glucose<ref name="Russell-2014"/>, so this study might be the result of the rather unusual structure.
<ref name="Schutz-1980">Y. Schutz, E. Ravussin, Respiratory quotients lower than 0.70 in ketogenic diets., Am J Clin Nutr, volume 33, issue 6, pages 1317-9, Jun 1980, PMID [http://www.ncbi.nlm.nih.gov/pubmed/7386422 7386422]</ref>
<ref name="Lambert-1994">EV. Lambert, DP. Speechly, SC. Dennis, TD. Noakes, Enhanced endurance in trained cyclists during moderate intensity exercise following 2 weeks adaptation to a high fat diet., Eur J Appl Physiol Occup Physiol, volume 69, issue 4, pages 287-93, 1994, PMID [http://www.ncbi.nlm.nih.gov/pubmed/7851362 7851362]</ref>
<ref name="VolekFreidenreich2016">Jeff S. Volek, Daniel J. Freidenreich, Catherine Saenz, Laura J. Kunces, Brent C. Creighton, Jenna M. Bartley, Patrick M. Davitt, Colleen X. Munoz, Jeffrey M. Anderson, Carl M. Maresh, Elaine C. Lee, Mark D. Schuenke, Giselle Aerni, William J. Kraemer, Stephen D. Phinney, Metabolic characteristics of keto-adapted ultra-endurance runners, Metabolism, volume 65, issue 3, 2016, pages 100–110, ISSN [http://www.worldcat.org/issn/00260495 00260495], doi [http://dx.doi.org/10.1016/j.metabol.2015.10.028 10.1016/j.metabol.2015.10.028]</ref>
<ref name="Figlewicz-2009">DP. Figlewicz, G. Ioannou, J. Bennett Jay, S. Kittleson, C. Savard, CL. Roth, Effect of moderate intake of sweeteners on metabolic health in the rat., Physiol Behav, volume 98, issue 5, pages 618-24, Dec 2009, doi [http://dx.doi.org/10.1016/j.physbeh.2009.09.016 10.1016/j.physbeh.2009.09.016], PMID [http://www.ncbi.nlm.nih.gov/pubmed/19815021 19815021]</ref>
<ref name="SRINIVASAN-1954">M. SRINIVASAN, IS. BHATIA, The carbohydrates of Agave vera cruz Mill. 2. Distribution in the stem and pole., Biochem J, volume 56, issue 2, pages 256-9, Feb 1954, PMID [http://www.ncbi.nlm.nih.gov/pubmed/13140183 13140183]</ref>
<ref name="Phinney-2011-p31">Phd Stephen D. Phinney MD, Rd Jeff S. Volek Phd, [http://www.amazon.com/The-Art-Science-Carbohydrate-Living/dp/0983490708 The Art and Science of Low Carbohydrate Living: An Expert Guide to Making the Life-saving Benefits of Carbohydrate Restriction Sustainable and Enjoyable], 2011, publisher Beyond Obesity LLC, isbn 978-0-9834907-0-8, Page 31</ref>
</references>
[[Category:Nutrition]][[Category:Science]]
