Fat vs Lean Gains in Athletes

This study looked at the body composition during weight increases and decreases in athletes (Silva AM, Matias CN, Santos DA, Rocha PM, Minderico CS, Thomas D, Heymsfield SB, Sardinha LB. Do Dynamic Fat and Fat-Free Mass Changes follow Theoretical Driven Rules in Athletes? .Med Sci Sports Exerc. 2017 Oct;49(10):2086-2092.). The results were startling:

Athletes that lost BW used 90% of the energy from FM while in those gaining BW, 95% was directed to FFM. When BW is lost, dynamic changes in its composition do not follow established rules and predictions used for lean or overweight/obese nonathletic populations.

Credit to Sigma Nutrition for this subject. Check out their podcasts.

CrossFit Competition – Festivus Games

Last month, I competed in my first CrossFit competition, the Festivus Games.

I did not do all that great but it was fun. And hard. Mostly hard. A little fun.

That’s 518th out of 666 entries. The only reason I placed that high is that I made it into the finals. The top five people in every box got into the finals and CrossFit Pittsburgh wasn’t all that crowded.


NSAIDs and Exercise Recovery

Here’s why I avoid NSAIDs after exercise (Sports Med. 2012 Dec 1;42(12):1017-28. The use of nonsteroidal anti-inflammatory drugs for exercise-induced muscle damage: implications for skeletal muscle development. Schoenfeld BJ.):

Exercise-induced muscle damage (EIMD) is a common condition resulting from a bout of vigorous exercise, particularly if the individual is unaccustomed to performance of the given movement. Symptoms of EIMD include delayed-onset muscle soreness (DOMS) and a loss of physical function.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are routinely prescribed post-exercise to alleviate these symptoms and restore normal physical function.

Of potential concern for those who use NSAIDs to treat EIMD is the possibility that they may impair the adaptive response to exercise. Specifically, there is emerging evidence that the action of cyclo-oxygenase (COX) enzymes, and COX-2 in particular, are important and even necessary to achieve maximal skeletal muscle hypertrophy in response to functional overload. Given that NSAIDs exert their actions by blocking COX and thus suppressing prostaglandin production, a theoretical rationale exists whereby these drugs may have detrimental effects on muscle regeneration and supercompensation. Therefore, the purpose of this article is to extensively review the literature and evaluate the effects of NSAIDs on muscle growth and development.

Based on current evidence, there is little reason to believe that the occasional use of NSAIDs will negatively affect muscle growth, although the efficacy for their use in alleviating inflammatory symptoms remains questionable. Evidence on the hypertrophic effects of the chronic use of NSAIDs is less clear. In those who are untrained, it does not appear that regular NSAID use will impede growth in the short term, and at least one study indicates that it may in fact have a positive impact.

Given their reported impairment of satellite cell activity, however, longer-term NSAID use may well be detrimental, particularly in those who possess greater growth potential.


Heart Rate Training (HRT) – Part 10

Part 1 of this series.

Dr Noakes to the Rescue?

I think we are trying to fit big feet into small shoes by trying to make Low Carb fit into exercise modes which are by design not compatible with being fat fueled.

I have great respect for Dr Noakes, but in my opinion the following video illustrates how we are missing the point when it comes to athletic performance and Low Carbohydrate diets.

Dr Noakes (@20:00) makes a startling comment in the video (@20:04).

There must be an exercise duration for which fat adaptation is the preferred state for optimal performance and I don’t know if we have found it yet…

Dr Noakes is humble in this video and admits that his own studies which showed advantages may have been biased – that was helpful for those of us who bought the hype that we can perform any sport on LC and do it well.

However, this video completely misses the point in a weird sort of way. People do low carb and get great benefits but find it doesn’t mix well with their particular athletic modality. In fact, they may find it doesn’t mix well with any competitive athletic modality. And, all athletics is artificial in some sense so to conclude that it is a bad diet based on some artificial measurement is missing the mark. Low Carb has found a home with triathletes and ultra-marathon runners but those are fairly elite choices.

What Dr Noakes is missing is that the real issue isn’t one of duration. The issue is one of fuel source. Certainly intensity and duration are inversely related. Sprints are intense and short. Ultra-marathons are low intensity but very long in duration. Few people want to do an ultra marathon.

We low carb athletic proponents are fond of touting the advantages of fat adaptation. It is true that the low carb athlete is better at accessing fuel but only out of necessity since the body spares carbohydrate stores on the low carb diet. The body doesn’t want to spend carbs on exercise since those stores are limited. But if you push your intensity up high enough it will pull from carb stores and these are limited in both depth and speed that can be accessed on a low carb athlete. This necessarily reduces exercise intensity to levels that are not competitive.

This is why folks who do Crossfit or take up wrestling find that they need to supplement carbohydrates. They chose to alter their diet to fuel their exercise rather than picking an exercise mode which matches their diet. Personally, I view this as a fundamental mistake.

What is the Answer?

The right answer is to engage in athletic activities which utilize the fat as fuel and don’t rely on carbohydrates as fuel. When a person is completely fat fueled they have a very deep tank of storage for energy. The use of fat as fuel necessarily translates to a reduced intensity which is problematic on any medium duration sports.

What intensity level is this done at? Here’s where some data can illustrate the point. Ben Greenfield published his own VO2max testing and I’ve plotted his VO2max numbers vs his RER numbers. (Remember that RER is a measure of fuel mixture. An RER of 0.7 indicates that the person is 100% fat fueled and an RER of 1.0 indicates a person is 100% carbohydrate fueled. An RER of 0.85 would be 50-50 mix of fat/carbs.)

Ben’s data is pretty jumpy so the red line is a 3rd order polynomial which is fitted to the data (the R^2 was 0.85). It shows a dip (more fat burning) at around 35% of VO2max. The data also shows a fairly flat line across the entire range from 25% to 50%. The actual data showing the dip is:

This is a very specific point in time where Ben Greenfield’s data showed him burning 97% of his energy from fat – clearly the sweet spot for a person who is fat fueled since almost none of the energy he was using came from carbs. Ben never got an RER below 0.7 so this is the best he did during that time. Unfortunately, that point is a pretty low point level of intensity. Well, sorta. Ben’s VO2max is 61.1 and that point was at a VO2 rate of 27.2 so the point where Ben was being as fat fueled as he possibly could be was at 45% of his VO2max.

This correlates well with other published data:

This shows a peak fat oxidation rate at 65% of VO2max but the issue isn’t one of maximum fat oxidation since at 65% the fat is mixed with carbohydrate oxidation. That does produce the most efficient exercise but only in a non-fat fueled athlete. The attractiveness of the data is that it clearly shows a fairly wide curve. The whole graph is relatively flat from 50% to 75%. But what is different between these two points is the fuel source in the body.

Fine Tuning Fat Burning

The spot is the highest intensity which can be reached where 100% of energy comes from fat and 0% from carbohydrates. I don’t know if there’s a term for this but let’s call it the Maximum Glucose Sparing/Fat Burning the MGSFB point.

I happen to know my MGSFB from my VO2max data. Here, I’ve added a bulls eye at the MGSFB point. At this point my RER was 0.7 and rising.

[Note for people trying to lose fat: I have no interest  at all in fat burning at this point in time but the implications of the above should be obvious for those who are interested in fat burning. You can get the most bang for the buck in fat burning at a level which is much less than your max heart rate. If you are beating yourself up in the gym that may be good news.]

My MGSFB was at 65% of my VO2max and it was at a HR. This matches the point at the top of the curve shown of fat oxidation rates vs VO2max. In fact, that could well be the very definition of fat adapted – ie, the ability to most efficiently burn fat at the highest VO2max point.

This was at a HR of 117 bpm. This correlates well to the center of the Maffetone HR value of 112-122 bpm. In fact, it might suggest that I should drop my range to 107-117 max since that guarantees I stay in the fat burning range for the entire activity

So how do you figure this out for yourself?

Here’s the approach I essentially took to get to this number:

  • Get fat adapted by adopting a Very Low Carb diet (< 30g of carbohydrates)
  • Do this for the TBD (days/weeks/months) adaptation period
  • Get your VO2max tested
    • If your VO2max doesn’t show you with an RER of 0.7 for a large portion of the test time you are not yet fat adapted
  • Plot the curve or just look at the data and find the highest point where your RER is still 0.7 or less
    • The point at which it goes over 0.7 you are no longer burning fat exclusively
  • Find the corresponding heart rate
    • That is your max heart rate for exercising

A Cheaper/Easier/Faster/Close-Enough Way

Just use the MAF calculation. It’s close enough. I like it enough that I wrote an MAF calculator and put it on-line here.


A Long Bike Ride

I took a look at a 3-hour long bike ride (Exercise Intensity on Low Carb) last month. I did the ride at a average heart rate of 138 bpm.

I took a longer ride later that same week and I have the data from that ride. How does the data from the ride compare to my recent thoughts on Heart Rate Training (HRT)? I did push myself as hard as I could on the ride. What I am interested in is the question in reverse. That is, if I push hard and long what was my heart rate?

From the HRT data and my own VO2max testing I know that my aerobic (fat fueled) zone is at a heart rate of 112-122 bpm. That means that at a higher heart rate (level of exertion) I am burning down my glycogen stores. (That is a problem if you are Low Carb.) After this long ride my blood sugar was pretty low (in the 50’s). Clearly from my blood sugar, I burned through my glycogen stores.

Trail Route

Here’s the trip I took along the Great Allegheny Passage Trail. I took the trip with my 14-year old son. I think I almost killed him. The GPS and heart rate data dropped out a couple of times along the way but here’s the map.

It was a long ride at almost 4 hours of riding. My speed at 8.8 mph was really slow. Here’s the details of the ride.

The data showed my average heart rate at 125 bpm. Hard to tell exactly where it was but here’s the graph that the program recorded. This was clearly an endurance event. The green line is approximately my MAF heart rate of 112-122 bpm. It is pretty close to the average of 125 bpm on the ride. The fact that there was activity above the line indicates that some portion of that activity was fueled by carbohydrates (glycogen stores).

Fat Oxidation Rates

That’s a total of 227 minutes and 1398 calories. This is a fat oxidation rate of 0.68 g/min (assuming all of the activity was fat fueled – which is wasn’t). That is very close to the rate noted here (Nutrition. 2004 Jul-Aug;20(7-8):716-727. Optimizing fat oxidation through exercise and diet. Achten J, Jeukendrup AE.).

With increasing exercise intensities, the fat oxidation rate increased to a maximum of 0.60 ± 0.07 g/min at 64 ± 4% VO2max (range 42-84), which corresponds to 74 ± 3% HRmax (range 54-92).

Future Plans

I want to repeat a long endurance ride with my heart rate limited at 112-122 bpm and see how my performance turns out.


Burning Fat During Exercise

Our bodies are hybrid engines which allows us to burn both fat and carbohydrates.

We are always running with a mix of fat and carbohydrates. After we eat a plate of pasta we are fueling ourselves with the carbohydrates. After we sleep we are being fueled with our body fat. The ability to switch between the two fuel sources is what makes it so we can sleep through the night without getting up every few hours to eat.

The holy grail for performance would be to burn fat and carbohydrates at the maximum possible rate and at the same time. For the Low Carb eater who has very little carbohydrate stores understanding how to perform eating a High Fat diet is important.

The human body has very little carbohydrate stores – about a day’s worth of fuel. The human body has nearly unlimited amounts of fat storage – many weeks worth of fuel in even the leanest person.

Running on Both Fuels at the Same Time

It turns out that eating carbohydrates during exercise reduces fat oxidation rates. Surprisingly, there’s a lot of theories on how this fat/carb balance works and the science it not settled on how this all works. Here’s a paper which is a good summary of how this might work (L. L. Spriet and M. J. Watt. Regulatory mechanisms in the interaction between carbohydrate and lipid oxidation during exercise. Acta Physiol Scand 2003, 178, 443–452).

During (low-moderate intensity) exercise in the fasted state adipose tissue lipolysis exceeded skeletal muscle fat oxidation, whereas CHO ingestion resulted in elevated plasma insulin, reduced adipose tissue lipolysis and decreased fat oxidation that equalled the reduction in lipolysis, thus indicating a limitation of FFA availability for fat oxidation.


Fat utilization increases from rest during low to moderate intensity exercise (40–65% VO2max), however, fatty acid oxidation decreases at power outputs above ~75% VO_ 2max (Romijn et al. 1993, Sidossis et al. 1997)

Takeaway to lose body weight exercise at levels  in that 40-60% of VO2max. If you exercise above that level it comes from glycogen stores. Either way, win-win.


High Performance Elite Athletes on Low Carb

Another study on exercise and ketogenic diets (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.).

Three weeks of intensified training and mild energy deficit in elite race walkers increases peak aerobic capacity independent of dietary support.

Adaptation to a ketogenic low carbohydrate, high fat (LCHF) diet markedly increases rates of whole‐body fat oxidation during exercise in race walkers over a range of exercise intensities.

The increased rates of fat oxidation result in reduced economy (increased oxygen demand for a given speed) at velocities that translate to real‐life race performance in elite race walkers.

In contrast to training with diets providing chronic or periodised high carbohydrate availability, adaptation to an LCHF diet impairs performance in elite endurance athletes despite a significant improvement in peak aerobic capacity.

Let’s ignore the shortness of the study for the sake of argument. The trade-off here is that when you burn more fat you require more oxygen for that burning.

…CHO as a substrate for muscle metabolism by virtue of an approx 8% higher energy yield per litre of oxygen (O2) consumed when CHO was the primary fuel oxidised.

This might explain the higher heart rates reported while exercising on Low Carb diets (Using Body Fat for Energy). I’ve seen this myself.

I am convinced there are exercise domains that Low Carb does great in but some it does not do as well. I think CrossFit is one of these. These are glycolytic sports but unless you are a world-class athlete does it really matter? And is it worth your health to compete at some of these elite levels?


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.


Exercise and Stress

There are plenty of sources of stress in our lives. Exercise both helps with stress and causes stress. Here’s a good survey of the subject (Expert Rev Endocrinol Metab. 2006 Nov 1; 1(6): 783–792.  Stress and the neuroendocrine system: the role of exercise as a stressor and modifier of stress. Anthony C Hackney, PhD, CPH).

From the summary:

  • Physical exercise is a stressor to the human body and serves as a robust activator of the neuroendocrine system, provided that the exercise is of sufficient volume (i.e., intensity and/or duration). The magnitude of the neuroendocrine stress response to exercise seems directly proportional to the volume of exercise exposure. These stress hormone responses are typically very transient in nature and do not last longer than a few minutes to hours into recovery.
  • Chronic exposure to exercise training results in adaptations in the neuroendocrine system, such that there is a reduction in hormonal stress response to submaximal exercise and, in many cases, reduced circulating basal stress hormone levels. This abatement of the hormonal stress response with exercise training has implications for dealing with many chronic stress-related health problems.
  • The adaptability and plasticity in the neuroendocrine system to exercise training has limits. Excessive exercise training can push the neuroendocrine exercise stress response to become inappropriate, resulting in the potential development of chronic fatigue and the overtraining syndrome condition.


Exercise Equipment

Cast Iron Kettlebells



Power Cage

Hyper/Back Extension Ab Bench

I got more out of my first time on one of these benches than four trips to the Chiropractor.

Pullup Bar