Glycogen Stores – Why does it matter?

From the study (K J Acheson Y Schutz T Bessard K Anantharaman J P Flatt E Jéquier. Glycogen storage capacity and de novo lipogenesis during massive carbohydrate overfeeding in man. The American Journal of Clinical Nutrition, Volume 48, Issue 2, 1 August 1988, Pages 240–247):

Glycogen storage capacity in man is approximately 15 g/kg body weight and can accommodate a gain of approximately 500 g before net lipid synthesis contributes to increasing body fat mass.

The question then comes up – what happens when you fill up the glycogen stores from carbohydrate consumption? That’s exactly the question that the study asked. And the answer they got was:

When the glycogen stores are saturated, massive intakes of carbohydrate are disposed of by high carbohydrate-oxidation rates and substantial de novo lipid synthesis (150 g lipid/d using approximately 475 g CHO/d) without postabsorptive hyperglycemia.

Some of it burns off (the “high carbohydrate-oxidation rates”) but a lot of it gets stored as fat via DNL (de novo lipogenesis). And the storage efficiency is pretty darned good. 150g of lipids are 1350 calories of fat. The 475g of carbs provides 1900 calories. So the efficiency is 71%.

Without High Blood Sugar Levels

The most amazing part is that all of this happens, per the study “without postabsorptive hyperglycemia”. In other words, the blood sugar doesn’t go high. It all happens within the liver.

The Test Subjects were young and their livers weren’t fat to begin with.

Second Study

Another study (Increased liver fat and glycogen stores after consumption of high versus low glycaemic index food: A randomized crossover study.
Stephen Bawden PhD Mary Stephenson PhD Yirga Falcone Melanie Lingaya Elisabetta Ciampi PhD Karl Hunter PhD Frances Bligh PhD Jörg Schirra PhD Moira Taylor. 4 September 2016).

Plasma glucose and insulin peak values and area under the curve were significantly greater after the HGI test meal compared with the LGI test meal, as expected. Hepatic glycogen concentrations increased more after the HGI test meal ( P < .05) and peak levels were significantly greater after 7 days of HGI dietary intervention compared with those at the beginning of the intervention ( P < .05). Liver fat fractions increased significantly after the HGI dietary intervention compared with the LGI dietary intervention (two‐way repeated‐measures analysis of variance P ≤ .05).

Compared with an LGI diet, a 1‐week HGI diet increased hepatic fat and glycogen stores. This may have important clinical relevance for dietary interventions in the prevention and management of non‐alcoholic fatty liver disease.

A Third Study

In this paper (Int J Sports Med. 1982 Feb;3(1):22-4. Muscle glycogen storage and its relationship with water. Sherman WM, Plyley MJ, Sharp RL, Van Handel PJ, McAllister RM, Fink WJ, Costill DL.):

This study examined the relationship between muscle glycogen and muscle water content. Exercise dietary manipulations were used to vary skeletal muscle glycogen levels in four groups of rodents: (1) eight animals were sedentary controls (SC); (2) ten animals were treadmill familiarized and allowed to recover 24 h before sacrifice (F); (3) ten animals were treadmill familiarized and exercised to exhaustion (E); (4) ten animals were treadmill familiarized, exercised to exhaustion, and allowed to recover with food and water ad libitum for 72 h (ER).

All animals were sacrificed in a resting state to normalize intracellular, extracellular, and interstitial water compartments; thus, the E group was sacrificed 45 m in following their run. The treatments altered skeletal muscle glycogen to values ranging from 10.0 to 30.2 mumol glucosyl units/g wet tissue weight. Neither muscle triglyceride nor protein levels were affected by the treatments.

Muscle water content expressed as mumol H2O lost/g wet tissue weight or made relative to protein content showed no consistent relationship to the glycogen content.

These data, therefore, do not support the commonly accepted muscle glycogen-to-water ratio of 1.0:2.7 (g:g). Further work is necessary to quantify the exact amount of water that is actually associated with the glycogen complex.

 Impressive Fourth Study

From (Eur J Appl Physiol. 2015 Sep;115(9):1919-26. doi: 10.1007/s00421-015-3175-z. Epub 2015 Apr 25. Relationship between muscle water and glycogen recovery after prolonged exercise in the heat in humans. Fernández-Elías VE1, Ortega JF, Nelson RK, Mora-Rodriguez R.):


On two occasions, nine aerobically trained subjects ([Formula: see text] = 54.4 ± 1.05 mL kg(-1) min(-1); mean ± SD) dehydrated 4.6 ± 0.2 % by cycling 150 min at 65 % [Formula: see text] in a hot-dry environment (33 ± 4 °C). One hour after exercise subjects ingested 250 g of carbohydrates in 400 mL of water (REHLOW) or the same syrup plus water to match fluid losses (i.e., 3170 ± 190 mL; REHFULL). Muscle biopsies were obtained before, 1 and 4 h after exercise.


In both trials muscle water decreased from pre-exercise similarly by 13 ± 6 % and muscle glycogen by 44 ± 10 % (P < 0.05). After recovery, glycogen levels were similar in both trials (79 ± 15 and 87 ± 18 g kg(-1) dry muscle; P = 0.20) while muscle water content was higher in REHFULL than in REHLOW (3814 ± 222 vs. 3459 ± 324 g kg(-1) dm, respectively; P < 0.05; ES = 1.06). Despite the insufficient water provided during REHLOW, per each gram of glycogen, 3 g of water was stored in muscle (recovery ratio 1:3) while during REHFULL this ratio was higher (1:17).


Our findings agree with the long held notion that each gram of glycogen is stored in human muscle with at least 3 g of water. Higher ratios are possible (e.g., during REHFULL) likely due to water storage not bound to glycogen.

Fifth Study
Another study (J. Bergström & E. Hultman (1967) A Study of the Glycogen Metabolism during Exercise in Man, Scandinavian Journal of Clinical and Laboratory Investigation, 19:3, 218-228).

The following inferences can be drawn from the results:

1. During work, the muscle glycogen falls successively to values approaching zero, and the working capacity decreases when the glycogen store is depleted.

2. The glycogen concentration in resting muscle remains unchanged when other muscle groups in the same subject have been emptied of glycogen by exercise.

3. If glucose is infused continuously during muscular work, the glycogen consumption is significantly lower than when no glucose is administered. The difference is nevertheless small, and the consumption of muscle glycogen is responsible for the greater part of the energy production, even when the blood sugar level is high.

4. The glucose production by the liver increases towards the end of continuous muscular work, but is of relatively small magnitude in comparison to the total carbohydrate metabolism.

Shorter Study Problems

Short studies have the problem that it takes time to saturate the body’s glycogen stores. For instance a four day long carbohydrate overfeed showed the phenomenon of glycogen fill (Minehira, Effect of Carbohydrate Overfeeding on Lipogenesis. OBESITY RESEARCH Vol. 11 No. 9 September 2003, p 1096).
Under standard isocaloric conditions, 42% of the ingested glucose was oxidized over the 5-hour postingestive period. The remaining 58% was essentially stored as glycogen (54%), with very little net de novo lipogenesis (4% of the glucose load).
After overfeeding:
Net nonoxidative glucose disposal was consequently reduced and represented only 43% of the glucose load. Simultaneously, net glycogen synthesis was reduced and represented only 30% of ingested glucose, whereas net de novo lipogenesis increased by 296% and corresponded to 13% of ingested glucose. There was also a marked increase in fasting and postprandial plasma TG concentrations after carbohydrate overfeeding together with suppressed plasma FFA concentrations. This increase in plasma TGs may be caused by both stimulation of hepatic de novo lipogenesis (18) and a decreased clearance of very-low-density lipoprotein-TGs.
Even that study shows increased DNL.
In conclusion, the present data indicate that whole body
de novo lipogenesis after glucose ingestion was markedly
enhanced by a 4-day carbohydrate overfeeding and that the
amount of lipid newly synthesized markedly exceeded the
maximal reported rates for hepatic de novo lipogenesis.
A Useful Strategy

So the useful strategy is to lower the glycogen stores via low carbohydrate diet and exercise. Both of these lower glycogen quickly and can begin to drop the fat in the liver. The fat around the pancreas can then begin to drop and diabetes gets reversed.


Glycogen Replenishment Strategies

Athletes who are carb fueled (glycogen stores provide their energy) try to optimize their carbohydrate consumption. They carb up before events like marathons, in order to have their stores at a maximum. This pushes out the time to bonk to later in the race. They take goo packs with them in races and feed themselves carbs during longer events to keep up their energy sources.

Optimizing these strategies are key. But how fast can glycogen stores be refilled? From this article (Glycogen Replenishment After Exhaustive Exercise):

The body stores approximately 450-550 grams of glycogen within the muscle and liver for use during exercise. At higher exercise intensities, glycogen becomes the main fuel utilized. Depletion of liver glycogen has the consequence of diminishing liver glucose output, and blood glucose concentrations accordingly. Because glucose is the fundamental energy source for the nervous system, a substantial decline in blood glucose results in volitional exhaustion, due to glucose deficiency to the brain.

Turns out it takes a whole lot of carbohydrates to replenish these reserves:

One study reported that a carbohydrate intake totaling up to 550-625 grams per day was found to restore muscle glycogen stores to pre-exercise levels within the 22 hours between exercise sessions. The findings of this study were supported by second study in which a carbohydrate intake of 3100 kcal resulted in complete resynthesis of glycogen within 24 hours.

Turns out that the rate of replenishment is quantified as well:

Normally, 2% of glycogen is resynthesized per hour after the initial 2 hours immediately after exercise. With administration of 50 grams of carbohydrate every 2 hours, the rate rose to 5% per hour, but did not rise when additional carbohydrate was administered. Administration of .7grams per kg body weight every two hours is another strategy that appears to maximize the rate of glycogen resynthesis. There is also some evidence that even smaller loads (28 grams every 15 minutes) may induce even greater repletion rates.

So here’s the math I see. Suppose you are in an athletic event consisting of several competitions spread out over several hours. If these events are spread out an hour between each event then the most replenishment you could get would be 5% per hour. That doesn’t seem like all that much to me and wouldn’t necessarily justify carb loading.

Now, I wouldn’t do carb loading anyway. I’d rather be fat fueled even if it does mean my performance is slightly less than it could be.

I’d rather have all my toes to exercise with than be a bit faster and not have my toes.

So What’s the Problem?

The problem is the nature of the foods consumed during refeeds are simple carbohydrates which have a higher Glycemic Index. These foods are known to not only refill Glycogen stores but increase liver fat (Diabetes Obes Metab. 2017 Jan;19(1):70-77. Increased liver fat and glycogen stores after consumption of high versus low glycaemic index food: A randomized crossover study. Bawden S, Stephenson M, Falcone Y, Lingaya M, Ciampi E, Hunter K, Bligh F, Schirra J, Taylor M, Morris P, Macdonald I, Gowland P, Marciani L, Aithal GP.).

Compared with an LGI diet, a 1-week HGI diet increased hepatic fat and glycogen stores. This may have important clinical relevance for dietary interventions in the prevention and management of non-alcoholic fatty liver disease.

Refill the glycogen stores with cupcakes and you get a fatty liver. Get a fatty liver and you get diabetes.


We All Are Hybrid Engines

A hybrid engine can run on more than one fuel. Hybrid cars run on electricity (from a battery) or gasoline (which charges the battery).

Turns out the human body is a hybrid engine. We can run on carbohydrates or fat. We can also run on Protein but it’s not efficient as a fuel (Glycogen Replenishment After Exhaustive Exercise).

The ability to switch between fuel sources is key to the ketogenic diet. Someone who is not fat fueled takes days to fully make the switch between fuel sources. But it turns out we are always running on a hybrid system regardless of whether or not we are ketogenic. For instance, overnight we are fasting until we eat and the carbohydrates in our system are depleted.

Similarly in exercise we switch from the various fuel systems in our body.  Athletes on High Carb (HC) and Low Carb (LC) diets were put onto a treadmill and run for hours. These curves show the metabolic flexibility of the LC diet.

The top graph is the rate that fat is oxidized (burned). The LC diet provides fat as a fuel very quickly and at a much higher level than the HC diet.

The bottom graph is the rate of carbohydrate oxidation. The LC diet doesn’t have the carb repositories (glycogen stores) that the HC diet has so they don’t get much energy from glycogen stores. However, unlike the HC diet the LC diet provides consistent amount of carb energy throughout the workout.The HC diet has a high level at the beginning but drops over time which results in the characteristic bonk of the long distance runner.

Note that even the HC diet eventually requires body fat for fuel. It just doesn’t have instant access to the fat like the LC diet.

What I Observe In the Gym

I do CrossFit for exercise. CrossFit is commonly viewed as a glycogen intensive sport (J Physiol. 2013 Sep 15; 591(Pt 18): 4405–4413. Muscle glycogen stores and fatigue. Niels Ørtenblad, Håkan Westerblad, and Joachim Nielsen).

A Typical CrossFit Workout

Today’s Workout of the Day (WOD) was:

That’s 21 minutes of Box Jumping, Push-ups, Burpees, Back Squats, Hang Cleans, and Up-Downs (Burpees without pushups). That’s fairly short (not like running a marathon. It also includes 3 sets of 30 Wall balls. Quite a good workout.

Why Do CrossFit?

Note, I said I do CrossFit for exercise – not for sport. I don’t care what my exercise times are at CrossFit. I care if I get an effective workout. And I measure effectiveness by the accepted standard of heart rate .

Heart Rate as Metric of Effectiveness of a Workout

From the Mayo Clinic Website:

Gauging intensity using your heart rate

Another way to gauge your exercise intensity is to see how hard your heart is beating during physical activity. To use this method, you first have to figure out your maximum heart rate — the upper limit of what your cardiovascular system can handle during physical activity.

The basic way to calculate your maximum heart rate is to subtract your age from 220. For example, if you’re 45 years old, subtract 45 from 220 to get a maximum heart rate of 175. This is the maximum number of times your heart should beat per minute during exercise.

Once you know your maximum heart rate, you can calculate your desired target heart rate zone — the level at which your heart is being exercised and conditioned but not overworked.

The American Heart Association and the Centers for Disease Control and Prevention recommend a general target heart rate of:

  • Moderate exercise intensity: 50 to about 70 percent of your maximum heart rate

  • Vigorous exercise intensity: 70 to about 85 percent of your maximum heart rate

My Own Results

Here’s my heart rate as recorded by my Samsung Gear Sport watch:

The first part (0-30 minutes) was a chipper (the coach tells you what to do) which included a whole lot of stuff (pushups, jumping jacks, forward lunges, PVC work, sit-ups, squats). That got my heat rate as high as 160 near the end. The rest period then let my heart drop to “normal” range. Then the WOD…

I am 57-years old. To calculate max heart rate the standard way is to subtract your age from 220. So my max heart rate is 163. I hit that rate during the workout and I felt it. I had to stop and breath/rest at spots.

At the end I had spent most of my time at 85% (138 in my case) or more of my max heart rate. But I had energy left to clean up and started cleaning up immediately. It wasn’t that I didn’t work out hard. It’s that I am not glycogen dependent.  (Heart Rate Calculator).

The different oxidation rates of carbs and fat may provide the reason why I  can work out at a high heart rate but not be depleted at the end of the workout.

Both oxidation charts are in grams but remember that a gram of fat contains 9 calories of energy and a gram of carbohydrates contains 4 calories of energy. And the repositories of glycogen are in the hundreds of grams total. That’s a calorie repository of around 1600 calories, give or take. And it starts to drop quickly over time.

The repositories of fat are in the many thousands of grams. If you have just 22 lbs of fat, that’s 10 kg of fat or 90,000 calories available. Fat energy stays pretty constant. That may explain why I can keep moving after the WOD ends.

I work out for the express purpose of depleting my glycogen stores.


STRRIDE-AT/RT – Exercise Study

I was considering dropping CrossFit in favor of a strength program when I came across an interesting study which compared Aerobic Training (AT) to Resistance Training (RT) for impact on Metabolic Syndrome (MS). (September 15, 2011, Volume 108, Issue 6, Pages 838–844. Comparison of Aerobic Versus Resistance Exercise Training Effects on Metabolic Syndrome (from the Studies of a Targeted Risk Reduction Intervention Through Defined Exercise – STRRIDE-AT/RT. Lori A. Bateman, Cris A. Slentz, PhD, Leslie H. Willis, MS, A. Tamlyn Shields, MS, Lucy W. Piner, MS, Connie W. Bales, PhD, RD, Joseph A. Houmard, PhD, William E. Kraus, MD.)

AT/RT induced a significant improvement in the MS z score (p = 0.004) and AT alone exhibited a trend toward improvement (p <0.07). However, RT alone failed to significantly alter the MS z score.

My conclusion is to stick with CrossFit and work in the resistance training as often as reasonable as an accessory to CrossFit.

Another view of the same data (J Appl Physiol (1985). 2015 Jun 15;118(12):1474-82. The effects of aerobic, resistance, and combination training on insulin sensitivity and secretion in overweight adults from STRRIDE AT/RT: a randomized trial. Abou Assi H, Slentz CA, Mikus CR, Tanner CJ, Bateman LA, Willis LH, Shields AT, Piner LW, Penry LE, Kraus EA, Huffman KM, Bales CW, Houmard JA, Kraus WE.). Conclusion:

AT/RT resulted in greater improvements in insulin sensitivity, β-cell function (disposition index), and glucose effectiveness than either AT or RT alone (all P < 0.05). Approximately 52% of the improvement in insulin sensitivity by AT/RT was retained 14 days after the last exercise training bout. Neither AT or RT led to acute or chronic improvement in sensitivity index. In summary, only AT/RT (which required twice as much time as either alone) led to significant acute and sustained benefits in insulin sensitivity.

Yet another look at the same data (Am J Physiol Endocrinol Metab. 2011 Nov;301(5):E1033-9. doi: 10.1152/ajpendo.00291.2011. Epub 2011 Aug 16.
Effects of aerobic vs. resistance training on visceral and liver fat stores, liver enzymes, and insulin resistance by HOMA in overweight adults from STRRIDE AT/RT. Slentz CA, Bateman LA, Willis LH, Shields AT, Tanner CJ, Piner LW, Hawk VH, Muehlbauer MJ, Samsa GP, Nelson RC, Huffman KM, Bales CW, Houmard JA, Kraus WE.) concluded:

AT was more effective than RT at improving visceral fat, liver-to-spleen ratio, and total abdominal fat (all P < 0.05) and trended toward a greater reduction in liver fat score (P < 0.10). The effects of AT/RT were statistically indistinguishable from the effects of AT. These data show that, for overweight and obese individuals who want to reduce measures of visceral fat and fatty liver infiltration and improve HOMA and alanine aminotransferase, a moderate amount of aerobic exercise is the most time-efficient and effective exercise mode.

Yet another view (Arch Intern Med. 2004 Jan 12;164(1):31-9. Effects of the amount of exercise on body weight, body composition, and measures of central obesity: STRRIDE–a randomized controlled study. Slentz CA1, Duscha BD, Johnson JL, Ketchum K, Aiken LB, Samsa GP, Houmard JA, Bales CW, Kraus WE.):

In nondieting, overweight subjects, the controls gained weight, both low-amount exercise groups lost weight and fat, and the high-amount group lost more of each in a dose-response manner. These findings strongly suggest that, absent changes in diet, a higher amount of activity is necessary for weight maintenance and that the positive caloric imbalance observed in the overweight controls is small and can be reversed by a modest amount of exercise. Most individuals can accomplish this by walking 30 minutes every day.

Note none of the results were comparable to the effect on the metabolic syndrome from the Low Carb High Fat diet.

Keto and CrossFit

It has been claimed that a Ketogenic diet is not compatible with CrossFit. The reasons most commonly given include:

  1. Some athletes who tried “low carb” have complained about performance losses
  2. CrossFit used to do Paleo and now does Zone
  3. CrossFit requires topped off Glycogen stores
  4. There are no high level athletes who consume a Ketogenic diet
  5. Ketogenic diet results in hormonal imbalances

I’d like to look at these claims one at a time.

Performance Losses on Low-Carb

Performance is a thing which is really hard to define. For CrossFit one definition of performance may be defined as the time to complete a particular combination workout such as Fran:

Three rounds, 21-15- and 9 reps, for time of:
95-pound Thruster

This is a very specific workout consisting of two movements. A Thruster is an Olympic weight lifting move down with a barbell loaded to 95 lbs total. Pull-ups are a body weight exercise with a form that is [more or less] particular to CrossFit.

The event is for time – faster is better.

The workout consists of 21-reps of the Thrusters followed by 21-reps of pullups are followed by 15 reps then 9 reps of each movement. The total time is considered the athlete’s “Fran time”.

Fran is picked as a representative set of movements and there are numerous other “benchmark” workouts (WODs) named after women (like hurricanes) and fallen warriers (the hero WODs).

These workouts allows a person to test and retest their performance over time. As a person gains strength and endurance their times will decrease (barring injury of course).

Judging Claims of Performance Losses

The claim, then, could be made that a low carb diet made someone’s Fran time longer. However, since Fran isn’t performed often it is hard to judge a diet based on Fran times and there are no studies offered of that particular metric. None of the athletes I’ve spoken with provided specific metrics for before and after the diet. Unlike other things in CrossFit which can be measured this claim is often more anecdotal than evidence based. This is important given CrossFit’s commitment to measurement as a gauge of improvement. From the man himself Greg Glassman: Understanding CrossFit:

the three most important and interdependent facets of any fitness program, can be supported only by measurable, observable, repeatable facts; i.e., data

Turns out that there actually is a specific study of this very subject. A randomized control trial (gold standard of science) was done at the James Madison University and took a mix of trained and untrained individuals and compared a group put on a Low Carb diet to another group who were not on a Low Carb diet (James Madison University. A low-carbohydrate ketogenic diet combined with six weeks of crossfit training improves body composition and performance. Rachel M. Gregory).  (Link to the complete study).

[2018-07-05 – Link to interview with Rachel on Keto for Normies podcast sheds additional light on the selection criteria.]

This study was done for the Masters Degree thesis of Rachel M Gregory in the Spring of 2016. Credit goes to BoxRox for uncovering this paper. The subjects of the study were:

Twenty-seven non-elite CrossFit subjects (mean ± SD age = 34.58 ± 9.26 years) were randomly assigned to a LCKD (males, n = 3; females, n = 9) or control (CON) (males, n = 2; females, n = 13) group.

LCKD (Low Carbohydrate Ketogenic Diet) was instructed to consume an ad libitum diet and restrict carbohydrate intake to less than 50 grams per day (<10% of total energy) and CON (Normal Diet) maintained usual dietary intake.

All subjects participated in four CrossFit training sessions per week during the 6 weeks.

The participants were measured through DEXA scans to determine body composition before and after. The results were:

Compared to the CON (Control) group, the LCKD (Low Carbohydrate Ketogenic Diet) group significantly decreased weight (0.18 ± 1.30, -3.45 ± 2.18 kg), BMI (0.07 ± 0.43, -1.13 ± 0.70 kg/m2), percent body fat (%BF) (0.01 ± 1.21, -2.60 ± 2.14%), and fat mass (FM) (0.06 ± 1.12, -2.83 ± 1.77kg), respectively. There was no significant difference in lean body mass (LBM) change between or within groups. We found no significant difference in total performance time change between the CON group and the LCKD group; however, both groups significantly decreased total performance time (CON: -41.20 ± 43.17 sec.; LCKD: -55.08 ± 44.29 sec.).

So the Low Carb group:

  • Lost more weight (about a lb a week)
  • Lost more body fat (as a percent)
  • Lost more fat mass (as lbs)

That’s not a surprise since the effectiveness of the ketogenic diet is well established. In fact, the control group actually gained a small amount of weight and body fat (the fat both as mass and a percentage). If you want to go CrossFit to lose weight, this study says it’s not going to happen. That matches the observations of some of the people I have gotten to know at CrossFit and fits other studies showing exercise doesn’t contribute much to weight loss (Diet Plus Exercise Equals Diet).

Since many and perhaps even most people get into Crossfit with the purpose of lowing weight this is a significant eye-opening finding. Six weeks of hard CrossFit with your old diet isn’t going to make you skinny.

But, Surely the Keto Dieters Performance Was Worse, Right

What is significant is the performance differences. The Low Carb group decreased their performance times (faster times) than the control group although the times were not statistically significant (because there were wide variations in both groups). The time difference (average) was 14 seconds better in the Low Carb group than the control group.

Since the scientific evidence doesn’t support performance differences how can I account for the claims of local athletes that they lost performance while on Low-Carb? The answer may be in what sort of diet these athletes were actually on.

The “Official” CrossFit Diet Used to be Paleo

Most of the athletes were on Paleo diets (Flexible Dieting: Why CrossFit Athletes are Ditching Paleo, June 23, 2016). The Paleo diet is usually a lower carb diet than the standard American Diet but it is not necessarily low carb.

For most people, the Paleo diet may not  be low enough carb to transition to fat adapted. I’ve taken a look at fat adaptation here. For example, if an athlete consumes too much fruit they may never become fat adapted. The fat adaptation process can take anywhere from weeks to months and in the transition it is widely known that performance can be lower. Additionally, cheating may result in a reset out of the ketogenic state which can take some time to re-enter. Basically, it’s a complete lifestyle change choice.

Robb Wolf states that Paleo diet:

is comprised of lean meats, seafood, fruits, vegetables, roots, shoots, tubers, nuts, and seeds.

In contrast, the Ketogenic diet excludes all fruit, many vegetables, roots, tubers and limits nuts and seeds. Each of the Paleo elements that are excluded in the Ketogenic diet are higher in carbohydrates. A Paleo person could eat potatoes and a Ketogenic person does not.

Since both diets exclude processed carbohydrates and grains they both lead to weight loss due to a net reduction in carbohydrates. Some of the people who eat Paleo also eat low enough amounts of carbohydrates to be in ketosis. Most probably don’t reach ketosis. To be in ketosis is to be fat fueled.

Failure to reach ketogenic levels is failure to access fat as the alternative fuel system.

Reference article

Glycogen as fuel

It is widely known that Ketogenic diets result in less glycogen stores in the liver and muscles. Glycogen is an energy source which can be used in intense workouts. So it would seem like having less glycogen would be a detriment in these intense sorts of workouts.

What this doesn’t take into account is that ketogenic athletes have an available fuel source that glycotic athletes lack quick access to – fat. The 6 ozs or so we have of glycogen have something like 600 calories worth of energy in them. The 30+ lbs of fat we typically have has over 100,000 calories of energy available. At least over a longer haul being fat adapted seems like a smart strategy.

For endurance athletes, being keto adapted has been well established as a benefit – see the FASTER study (Metabolism, March 2016. Metabolic characteristics of keto-adapted ultra-endurance runners. Volek, et. al.).

Peak fat oxidation was 2.3-fold higher in the LC group (1.54 ± 0.18 vs 0.67 ± 0.14 g/min; P = 0.000) and it occurred at a higher percentage of VO2max (70.3 ± 6.3 vs 54.9 ± 7.8%; P = 0.000). Mean fat oxidation during submaximal exercise was 59% higher in the LC group (1.21 ± 0.02 vs 0.76 ± 0.11 g/min; P = 0.000) corresponding to a greater relative contribution of fat (88 ± 2 vs 56 ± 8%; P = 0.000).

As to the glycogen stores:

Despite these marked differences in fuel use between LC and HC athletes, there were no significant differences in resting muscle glycogen and the level of depletion after 180 min of running (−64% from pre-exercise) and 120 min of recovery (−36% from pre-exercise).

Given that the glycogen stores in the Low Carb group were half of those in the high carb group just how relevant is the glycogen sparing effect? If two people go out to eat and one has $5 and the other had $15 and they both leave with $2.50 in their pocket could you say that the person who got less food was cash sparing? The energy comes from somewhere.

Also, the FASTER study was done at a lower %VO2max, ie, it was on a three hour endurance test, not a Crossfit 20 minute workout.

But is fat as quickly accessible as Glycogen?

Turns out fat is also very quickly accessible in these high-level fat adapted athletes. The FASTER study (Volek, et. al) compared the rte of fat and carbohydrate oxidation for the same 150 minute treadmill run. HC is High Carb and LC is Low Carb.

It is worth taking note that this study was done at a relatively low %VO2max level of effort. This contrasts with Crossfit workouts which are often done at higher intensity levels.

No Ketogenic Athletes

Given the public excommunication of Robb Wolf within CrossFit it’s not much of a surprise that there are not many top athletes who say they follow a Paleo or Ketogenic diet. That would hardly earn them the endorsement of top CrossFit personalities.

Also, these are people who would risk their health for the sake of winning (CrossFit and Steroids. Just How Juiced Is CrossFit? by John Romano | 10/16/15). If they think they can beat out the next guy by a second or two on Fran they will.

But this raises the question. Suppose it is determined that a ketogenic diet does affect performance by some small amount. A top athlete is dealing with very small percentages between herself and the next gal and is willing to risk their health. Is that the case for the average box-goer?

Also, given the very high level of training that goes into making a top CrossFit athlete they probably have a lot of wiggle-room in diet. They are burning it all off. But how many of us who do a 20 minute WOD a few days a week are doing anything like what these athletes are doing? And why should we follow their diets if we are not doing the same intense workout program?

Diet of the World’s Most Fit Woman

Digging around on the Interwebs for the diet of Katrin Davidsdottir, the winner of the 2015 CrossFit Games turns up this (This Is What the ‘Fittest Woman on Earth’ Eats Every Day  How does your diet stack up? by EMILY ABBATE August 10, 2015):

I’ve got to have my eggs, otherwise my day starts off wrong,” she says. “In an effort to get more fat in my diet for fuel, I eat half of the avocado and then the cream in my coffee.

On a good day, when she gets to eat lunch, it’ll be chicken salad and the other half of the avocado. On the days she doesn’t? “I’ll eat as soon as I finish training, and leave practice drinking coconut water with a scoop of chocolate protein powder and a serving of fruit. For dinner, I try to eat lots of dark green stuff-spinach, kale, broccoli. For protein I’ll have chicken. For dinner, which would come soon after that late lunch, I try to eat a portion of salmon for its healthy fats and vitamin D.”

Other than the single serving of fruit her diet is ketogenic. And given her workout schedule that’s not a whole lot of carbohydrates. Note that was back in 2015 (Robb Wolf’s split from CrossFit was about 2009) so this is long after that split.

So at least the world’s most fit woman eats a diet very much like a ketogenic diet, even if she doesn’t call it that.

Keto and Hormones

I am going to do a followup article on this subject.


Body Recomposition Series

My Body Recomposition series is on my Low Carb Studies BLOG.

In the series I set a number of goals for my body composition and means to achieve the goals. Looking back I did really well at hitting what were very aggressive goals.

  1. Improve HbA1C number (HbA1C is a lab test which shows the Blood Sugar over the previous three months)
    Goal: < 5.6 (Below bottom of Pre-Diabetic levels)
    I achieved 5.2 which is non-diabetic.
  2. Lose weight to reach 15% Body Fat (Visualize Body Fat percentages)
    I ended up at 7.5% body fat per Bod Pod.
  3. Barring any injury, be able to do exercise throughout entire test (CrossFit)
    Submaximally is OK (<85% of max level)
    I did this goal through June 2018 but was not able to exercise at a low enough level due to the competitive nature of Crossfit.
  4. Conserve current LBM (Lose Weight but not muscle)
    Possibly add LBM?
    Bod Pod shows I did gain LBM over that period.
  5. Maintain current metabolic levels.
    The same thing as saying not to eat at a net calorie deficit.
    I think the goal was correct (my TDEE is equal to my pre-diet TDEE due to higher exercise energy expenditure). But I had to have been at a significant caloric deficit because I lost quite a bit more weight.


The Cori Cycle – Not a new kind of bicycle (from Aug 2017)

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).


Thoughts on Exercise from Aug 2017

I’ve edited the following since I’ve learned a lot about exercise since I originally wrote the post (August 2017).

My Original Goal

At the start of this experience my goal was to Hack My Type Two Diabetes. Per my MD, I am no longer a diabetic and am just at the bottom end of the Pre-Diabetes range. So mission accomplished???

[2018-06-29 update – My last HbA1C was 5.2 which is no longer even pre-diabetic but right in the middle of the “normal blood sugar range.]

Are We There Yet?

My initial theory was that Diabetes is just a symptom of the underlying condition which is Insulin Resistance. Eating Low Carb. Moderate Protein and High Healthy Fats reduces the need for the body to produce Insulin but does it cure Insulin Resistance itself?

[2018-06-29 update -There is a need to differentiate between insulin resistance due to diabetes and peripheral insulin resistance due to a low carb diet. An Oral Glucose Tolerance Test (OGTT) may or may not be able to distinguish the two. Some people say it takes a time of reintroducing carbs before taking an OGTT.]

What is Insulin Resistance?

Insulin Resistance is the inability of the body’s cells to take in glucose in the presence of Insulin. From Skeletal Muscle Insulin Resistance Is the Primary Defect in Type 2 Diabetes.

Under euglycemic hyperinsulinemic conditions, ∼80% of glucose uptake occurs in skeletal muscle

If your muscles are not able to efficiently take up glucose then you have Insulin Resistance. It may be that exercise is the only way to improve glucose uptake in the muscles.

[2018-06-29 update -I believe that still to be the case but with the added thought that a low carbohydrate diet causes peripheral insulin resistance. Your muscles resist the action of glucose in a state where Insulin is low so that the glucose can be conserved (some say spared) for the essential parts of the body (brain, etc) that require glucose).]

Types of Exercise

When it comes to improving Insulin Resistance, I think there may be a difference between the sorts of exercise, ie, aerobic and anaerobic exercise. Repeatedly dumping all of the glucose out of the cells is part of what is needed to increase insulin sensitivity. That seems like where High Intensity exercise comes into play. Things like rapid reps of high weights vs walking on a treadmill.
[2018-06-29 update -Change this from “may be a difference” to “is a difference”. A year of CrossFit showed me the difference. I will write a post on it – or a hundred posts on it.]

My Experience with Exercise

This would bear out with my own experience of the quick dump of glucose that I experienced in the high intensity workout. My glucose went up at least 80 points which I now think is due to Insulin Resistance.

[2018-06-29 update -It was almost certainly peripheral insulin resistance plus workouts at high intensities mobilize a whole lot of carbohdyrates – perhaps as much as 60g/hr. That’s a whole lot of sugar dumped into the blood stream. And my body doesn’t do all that well with that much sugar. Although I will say it got better with time. Until I quite Crossfit that is.]

Not only is the liver dumping in that case but the muscles are dumping too. And that’s a good thing.

[2018-06-29 update -Turned out that the muscles don’t dump into the bloodstream. Only the liver does that. Learning more every day about this.]

So perhaps if I got this right it’s more about the type of exercise when attempting to improve the underlying Insulin Resistance than it is about the exercise itself. Is it true to say the reason my blood sugar rises so high with high intensity exercise is that my muscle cells are still Insulin Resistant and that with more exercise they will get better at responding to the Insulin they are given and then I will not see high blood sugar spikes during and immediately after exercise?

[2018-06-29 update -See comments earlier about peripheral insulin resistance.]

If I have this right I should easy be able to measure and observe progress by checking my blood sugars after exercise to exhaustion and the levels should drop.

I wish I had done those measurements more often and recorded the data.

Here’s a pretty good 2014 article on the subject. [2018-06-29 update – The article did not deal with the blood sugar of diabetics. I wish I had bothered to think more about this but was happy enough with my HbA1C numbers that I didn’t care.]

So why LCHF and Fasting?

Using LCHF + Fasting has helped me get to a weight where my pulse rate is lower, the stress on my joints is lower, my BP is lower and I am now at the point where I can safely exercise. Surely my Insulin Resistance is somewhat better but the only real way to attack it that is left is with high intensity exercise.
[2018-06-29 update – That’s when I took up Crossfit which I did for almost a year.]