I had an interesting response to intense exercise the other day. I was many days fasted and went to an introductory CrossFit class. I measured my blood sugar after I got home from the class and my blood sugar was around 80 points higher. Did some digging to try and find out why.
My first assumption was that the liver was dumping glycogen and that’s partly true. Turns out that the muscles store around 80% of our glycogen stores and the liver contains the rest. The muscles use the glycogen locally and they don’t dump glucose into the blood stream. All of the glucose does come from the liver which takes it out of stored glycogen. That would account for some of the rise. I usually see a ten point pop with some exercise like bike riding but not like that time. The CrossFit exercise was very hard compared to normal exercise.
Here’s where the the Cori Cycle comes into play. I was fasted during the exercise for more than 20 days. From the Wikipedia article:
The Cori cycle is a much more important source of substrate for gluconeogenesis than food. The contribution of Cori cycle lactate to overall glucose production increases with fasting duration. Specifically, after 12, 20, and 40 hours of fasting by human volunteers, the contribution of Cori cycle lactate to gluconeogenesis is 41%, 71%, and 92%, respectively.
This was a piece of data which I didn’t have before. This makes sense of the experience that I had with intense exercise. The muscles released a lot of lactate which at the end of the exercise gets converted in the liver through gluconeogenesis into glucose. Hence, the large pop in blood sugars.
[2018-06-29 – I think this is a pretty good explanation of the problem. I wish I knew more at the time about VO2max and Heart Rate Training. I could have picked the right mode of exercise (top of aerobic range) rather than the HIIT mode of Crossfit.]
Here is a great discussion of exercise and the Type 2 Diabetic with Dr Finney (Shelley. Low-Carb preserves Glycogen better than High Carb. Me and My Diabetes. April 14, 2011).
I’ve edited the following since I’ve learned a lot about exercise since I originally wrote the post (August 2017).
This will be an accumulated list of exercise related studies.
Athletic performance on Low Carb
- Metabolism Volume 32, Issue 8, August 1983, Pages 769-776. The human metabolic response to chronic ketosis without caloric restriction: Preservation of submaximal exercise capability with reduced carbohydrate oxidation. S. D. Phinney, B. R. Bistrian, W. J. Evans, E. Gervino, G.L. Blackburn.
- J Clin Invest. 1980;66(5):1152–1161. Capacity for Moderate Exercise in Obese Subjects after Adaptation to a Hypocaloric, Ketogenic Diet. Stephen D. Phinney, Edward S. Horton, Ethan A. H. Sims, John S. Hanson, Elliot Danforth Jr., and Betty M. Lagrange.
- Nutrients. 2014 Jun 27;6(7):2493-508. The effects of a ketogenic diet on exercise metabolism and physical performance in off-road cyclists. Zajac A, Poprzecki S, Maszczyk A, Czuba M, Michalczyk M, Zydek G.
- Exercise and Ketosis, Peter Attia
- Nutr Metab (Lond). 2004; 1: 7. Metabolic aspects of low carbohydrate diets and exercise. Sandra J Peters and Paul J LeBlanc.
- Med Sci Sports Exerc. 1998 Dec;30(12):1677-83. Effects of high fat versus high carbohydrate diets on plasma lipids and lipoproteins in endurance athletes. Brown RC, Cox CM.
- Hofmann, Peter & Lamprecht, M & Schwaberger, G & Pokan, Rochus & Von Duvillard, Serge. (2001). Effect of dietary modifications on lactate performance curve in incremental exercise tests and blood lactate concentration during endurance exercise on the cycle ergometer – A single case study. 110. 82-87.) which looked at Lactic Acid on three diets (Normal, Low Carb, High Carb).
- Journal of applied physiology (Bethesda, Md. : 1985). 88. 1707-14. Substrate metabolism during different exercise intensities in endurance- trained women. Romijn, Johannes & Coyle, Edward & Sidossis, Labros & Rosenblatt, J & Wolfe, R.R. 2000.
- J Physiol. 1996 Apr 1; 492(Pt 1): 293–306. Interaction of training and diet on metabolism and endurance during exercise in man. J W Helge, E A Richter, and B Kiens.
- Journal of Physiology, Volume 595, Issue 9, 1 May 2017, Pages 2785-2807. Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. Louise M. Burke Megan L. Ross Laura A. Garvican‐Lewis Marijke Welvaert Ida A. Heikura Sara G. Forbes Joanne G. Mirtschin Louise E. Cato Nicki Strobel Avish P. Sharma John A. Hawley.
- The Zone Diet and Athletic Performance. Sports Medicine, April 1999, Volume 27, Issue 4, pp 213–228. Samuel N. Cheuvront.
Exercise and Diabetes
- Nutrients. 2017 Feb 20;9(2). pii: E167. Fructose and Sucrose Intake Increase Exogenous Carbohydrate Oxidation during Exercise. Trommelen J, Fuchs CJ, Beelen M, Lenaerts K, Jeukendrup AE, Cermak NM, van Loon LJ.
- Acta Med Scand Suppl. 1986;711:55-65. Effects of Exercise on Glucose Tolerance and Insulin Resistance . Brief review and some preliminary results Effects of exercise on glucose tolerance and insulin resistance. Holloszy JO, Schultz J, Kusnierkiewicz J, Hagberg JM, Ehsani AA.
- Ethiop J Health Sci. 2016 Sep; 26(5): 409–414. Insulin Sensitivity and Plasma Glucose Response to Aerobic Exercise in Pregnant Women at Risk for Gestational Diabetes Mellitus. Heba Embaby, Enas Elsayed, and Mohamed Fawzy.
- Metabolism. Volume 32, Issue 6, June 1983, Pages 552-557. Metabolism
Daily variations of plasma glucose and insulin in physically-trained and sedentary subjects. Jacques Le Blanc, Angelo Tremblay, Denis Richard, André Nadeau.
Exercise Physiology (Mechanisms)
- Department of Health Sciences, Coordinator of Exercise and Fitness Program, School of Arts and Sciences, University of Bridgeport, 169 University Avenue, Bridgeport, CT 06604, USA. Skeletal Muscle Glycogen Depletion and Recovery During Four Consecutive Days of Prolonged Lift and Carry Exercise. Thomas B. Price and David M. Brady.
- European journal of applied physiology and occupational physiology. 57. 192-7. Lactate threshold and onset of blood lactate accumulation during incremental exercise after dietary modifications. Quirion, A & R Brisson, G & Laurencelle, L & DeCarufel, D & Audet, A & Dulac, S & Ledoux, Marielle & Vogelaere, P. (1988).
- Sports Med. 2014; 44(Suppl 1): 87–96. New Insights into the Interaction of Carbohydrate and Fat Metabolism During Exercise. Lawrence L. Spriet.
- Nutrition. 2004 Jul-Aug;20(7-8):716-727. Optimizing fat oxidation through exercise and diet. Achten J, Jeukendrup AE.
- Med Sci Sports Exerc. 2017 Jan;49(1):133-140. Maximal Fat Oxidation Rates in an Athletic Population. Randell RK, Rollo I, Roberts TJ, Dalrymple KJ, Jeukendrup AE, Carter JM.
- The American Journal of Clinical Nutrition, Volume 70, Issue 3, 1 September 1999, Pages 560s–569s. Essential fatty acids in health and chronic disease. Artemis P Simopoulos.
- Acta Physiol Scand 2003, 178, 443–452 Regulatory mechanisms in the interaction between carbohydrate and lipid oxidation during exercise. L. L. Spriet and M. J. Watt.
- Eur J Appl Physiol. 2010 Mar;108(4):791-800. Increased p70s6k phosphorylation during intake of a protein-carbohydrate drink following resistance exercise in the fasted state. Deldicque L1, De Bock K, Maris M, Ramaekers M, Nielens H, Francaux M, Hespel P.
- American Journal of Physiology-Endocrinology and MetabolismVol. 288, No. 4. 1 APR 2005. Combined ingestion of protein and free leucine with carbohydrate increases postexercise muscle protein synthesis in vivo in male subjects. René Koopman, Anton J. M. Wagenmakers, Ralph J. F. Manders, Antoine H. G. Zorenc.
- American Journal of Physiology-Endocrinology and Metabolism, Vol. 293, No. 3. 1 SEPT 2007. Coingestion of carbohydrate with protein does not further augment postexercise muscle protein synthesis. René Koopman, et.al.
- Medicine and Science in Sports [01 Jan 1979, 11(1):1-5]. Effects of preexercise feedings on endurance performance. Foster C , Costill DL , Fink WJ.
- J Strength Cond Res. 2002 Feb;16(1):50-7. The acute 1-week effects of the Zone diet on body composition, blood lipid levels, and performance in recreational endurance athletes. Jarvis M1, McNaughton L, Seddon A, Thompson D.
The Low Carb Studies BLOG is being split into two sites. The original Low Carb Studies BLOG will concentrate on the Low Carb/Ketogenic diet. This site will focus on Athletics on the Ketogenic Diet.
It will take a while to move the content over but allow more focus on each subject individually.