Is it the Low Carb or the High Fat?

Interesting study took a look at the question of whether it is high fat or low carb (Leckey JJ, Hoffman NJ, Parr EB, Devlin BL, Trewin AJ, Stepto NK, Morton JP, Burke LM, Hawley JA. High dietary fat intake increases fat oxidation and reduces skeletal muscle mitochondrial respiration in trained humans. FASEB J. 2018 Jun;32(6):2979-2991.) (Full PDF).

High dietary fat intake increases fat oxidation and reduces skeletal muscle mitochondrial respiration in trained humans.

It’s not a surprise that your body will burn more fat when you consume less carbohydrates. The Food Quotient (Food Quotient) predicts exactly that.

Mitochondria respiration (Mitochondrial Respiration) is:

…the set of metabolic reactions and processes requiring oxygen that takes place in mitochondria to convert the energy stored in macronutrients to  adenosine triphosphate(ATP), the universal energy donor in the cell.

I don’t know enough to know whether or not reduced mitochondrial respiration is good or bad for athletic performance. It seems like reduced rates of ATP would be bad for energy but is that energy made up in other ways? Is the loss offset by the increase in BHOB (ketone bodies)?

 

Fasted Workouts and 24 Hour Fat Oxidation

Fasted workouts cause increased 24 hour fat oxidation (Iwayama K, Kurihara R, Nabekura Y, et al. Exercise Increases 24-h Fat Oxidation Only When It Is Performed Before Breakfast. EBioMedicine. 2015;2(12):2003-2009).

Under energy-balanced conditions, 24-h fat oxidation was increased by exercise only when performed before breakfast. Transient carbohydrate deficits, i.e., glycogen depletion, observed after morning exercise may have contributed to increased 24-h fat oxidation.

These results probably don’t hold true for low carb athletes since our glycogen stores are probably already somewhat depleted.

MCT Oil and Athletic Performance

I read a post by a guy in a Facebook group who claims MCT oil increases his athletic performance. I questioned him and he wrote:

However, when the body fat percentage gets low, you need the fats for energy to fuel your workouts. You have to reach steady state of fat in and fat/ketones out. I don’t think I could do my noon workout without my two cups of BPC in the morning. That’s my fuel…

When I asked if it was the MCT oil or the caffeine he replied:

… it’s the fat. Caffeine does not give you the ketones that allow me to lift heavy and do 30-45 mins of elliptical. Although, when I was very fat, my body provided the fat ketones. So in a sense I’m agreeing with you. There comes a time when you need that MCT fat that the liver turns into ketones as a priority.

Unfortunately the science doesn’t back up the claims.

Study #1

Miriam E. Clegg. (2010). Medium-chain triglycerides are advantageous in promoting weight loss although not beneficial to exercise performance. International Journal of Food Sciences and Nutrition, 61:7,653-679.

Results indicate that MCT feeding is ineffective in improving exercise performance and future work should focus on the health benefits and applications of MCT.

Study #2

Damien J. Angus, Mark Hargreaves, Jane Dancey, and Mark A. Febbraio. Effect of carbohydrate or carbohydrate plus medium-chain triglyceride ingestion on cycling time trial performance. Journal of Applied Physiology. Volume 88 Issue 1. January 2000. Pages 113-119 .

These data demonstrate that carbohydrate ingestion during exercise improves 100-km TT performance compared with a sweet placebo, but the addition of MCT does not provide any further performance enhancement.

Study #3

A E Jeukendrup, J J Thielen, A J Wagenmakers, F Brouns, W H Saris; Effect of medium-chain triacylglycerol and carbohydrate ingestion during exercise on substrate utilization and subsequent cycling performance. The American Journal of Clinical Nutrition, Volume 67, Issue 3, 1 March 1998, Pages 397–404.

…ingestion of MCT had a negative effect on performance…

compared with placebo ingestion, MCT ingestion had no effect on total rates of fat or carbohydrate oxidation, nor did it affect exogenous or endogenous carbohydrate utilization. The negative effect of MCT ingestion was associated with increased gastrointestinal complaints (ie, intestinal cramping). These data suggest that large amounts of MCTs (85 g) ingested during prolonged submaximal exercise may provoke gastrointestinal problems leading to decreased exercise performance.

Study #4

Jeukendrup, A. E., A. J. M. Wagenmakers, F. Brouns, D. Halliday and W. H. M. Saris. Effects of carbohydrate (CHO) and fat supplementation on CHO metabolism during prolonged exercise. Metabolism 45(7): 915-921: 1996.

It is concluded that 29 g MCT co-ingested with CHO during 180 minutes of exercise does not influence CHO utilization or glycogen breakdown.

Other Studies

Another study found that MCT Oil increased liver size by adding fat to the liver (MCT Oil and Liver Size).

Train Low, Compete High

One popular Low Carb strategy is to train low and compete high. The basic strategy is to do all training in a fat adapted state and then switch to a higher carb state a day or two before competition.  A study took a look at this methodology (Havemann L, West SJ, Goedecke JH, Macdonald IA, St Clair Gibson A, Noakes TD, Lambert EV. Fat adaptation followed by carbohydrate loading compromises high-intensity sprint performance. J Appl Physiol 2006 Jan;100(1):194-202.). The study consisted of six days of High Fat diet to a High Carb diet on the 7th day. The study looked at the performance on the 8th day. The purpose of the carb fueling was to fill glycogen stores before the final tests.

The ingestion of a HFD for 6 days resulted in a shift in substrate metabolism toward a greater reliance on fat and a reduction in CHO oxidation. The increase in fat oxidation in the present study persisted despite 1 day of CHO loading on day 7 as demonstrated by the lower resting RER (0.77  0.02 vs. 0.88  0.05, Fig. 2) and higher circulating FFA (Table 7) during exercise after HFD-CHO compared with HCD-CHO on day 8.

Here’s what was valuable about this 2006 study.

The study is unique in that it is the first study to investigate the effect of high-fat feeding, followed by CHO loading, on endurance exercise, including high-intensity sprints that simulate actual race situations.

In spite of being on a High Carb diet the effects of the High Fat diet persisted. This could be seen in a lower RER value indicating increased fat oxidation. However, the sprint performance was not as good. From the discussion:

It was hypothesized that the potential glycogen-sparing effect of this dietary strategy (3) would be most beneficial for exercise that included high-intensity sprint bouts, where muscle glycogen is the predominant fuel. However, in contrast to our hypothesis, the HFD-CHO strategy actually compromised high-intensity 1-km sprint performance.

 

VESPA and FASTER

Vespa has a graph on their site that shows %VO2max vs Fat oxidation in Low Carb and High Carb athletes from the FASTER study (Fat Adaptation: The Emerging Science from FASTER). Here’s the chart as it appears on the Vespa site:

I can’t find this graph in the FASTER Study paper  (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, March 2016, Pages 100-110.).

But I do have some of the VO2max data tests from two of the athletes; Ben Greenfield and Damian Stoy. And Ben was LCD and Damian was HCD. So we should be able to check the graph using their data.

Here is Ben’s curve:

Here is Damian’s curve:

Peak Values

Damian’s peak rate of fat oxidation at around 0.35 g/min was about one-third of Ben’s top rate of around 1.1 g/min. So in this regard the curves do match the relative magnitudes in the Vespa graph.

Shifted Values?

The VESPA graph for the LCD vs the HCD shows a shift to the right for the peak fat oxidation for LCD as compared with HCD. In fact, the VESPA graph shows the peak of the LCD at 70% of VO2max and shows the peak of the HCD at 50%.

This doesn’t match Ben’s data at all. Ben’s fat oxidation peak is clearly around 55% of VO2max.

There is a small shift to the left for vegan Damian Stoy. His peak is somewhere around 45%.

I want to see the other data to see if Ben is at one end of the LC data but he pretty clearly doesn’t match the %VO2max vs maximum fat oxidation rate that the VESPA graph implies.

Why Should I Care?

I care because my own data matches Ben Greenfield’s data.

Slower But Fitter?

An interesting study put a group of endurance athletes on a Ketogenic diet and measured their performance as well as body composition changes (Zinn C, Wood M, Williden M, Chatterton S, Maunder E. Ketogenic diet benefits body composition and well-being but not performance in a pilot case study of New Zealand endurance athletes. J Int Soc Sports Nutr. 2017 Jul 12;14:22.). The study concluded:

All athletes increased their ability to utilise fat as a fuel source, including at higher exercise intensities.

Mean body weight was reduced by 4 kg ± SD 3.1 (p = 0.046; effect size (ES):0.62), and sum of 8 skinfolds by 25.9 mm ± SD 6.9; ES: 1.27; p = 0.001).

But how was their performance?

Mean time to exhaustion dropped by ~2 min (±SD 0.7; p = 0.004; ES: 0.53). Other performance outcomes showed mean reductions, with some increases or unchanged results in two individuals (VO2 Max: -1.69 ml.kg.min ± SD 3.4 (p = 0.63); peak power: -18 W ± SD 16.4 (p = 0.07), and VT2: -6 W ± SD 44.5 (p = 0.77).

Was this an adaptation problem?

Athletes reported experiencing reduced energy levels initially, followed by a return of high levels thereafter, especially during exercise, but an inability to easily undertake high intense bouts. Each athlete reported experiencing enhanced well-being, included improved recovery, improvements in skin conditions and reduced inflammation.

In the end the athletes likes the health benefits even with the performance losses.

FASTER Study Interviews

Zach Bitter was a participant of the FASTER study (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, March 2016, Pages 100-110.) Our BLOG post about Zach in the study (Zach Bitter – Another FASTER participant). Jeff Volek was one of the scientists doing the FASTER study. Endurance Planet interviewed them together in a three part series.

Jeff and Zach speculated about how long this could go saying that perhaps 5 hours would have been a better test. Based on Ben’s fat oxidation rate I’m not sure that would have been a good idea. Ben’s fat was dropping in a linear form but his carbohydrate oxidation was speeding up fits to a 2nd order poly.

Here is another interview with Zach about FASTER (Primal Endurance Podcast).

FASTER10 – Ben Greenfield – Three Hour VO2 testing

The main test that Ben test was a three hour treadmill test in the FASTER study (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, March 2016, Pages 100-110.).

In Ben Greenfield’s case the activity was done at an average of 60% of VO2max. At that level of effort Ben got 85% of his energy from fat and 15% from carbohydrates. Here’s the data from the three hour treadmill test.

%VO2max FATcal CHOcal %cal-fat
58% 10.013 3.1007 76%
61% 12.394 1.2341 91%
59% 11.722 1.4985 89%
60% 11.645 1.8409 86%
61% 11.154 2.5325 81%
Average = 60% 11.386 2.046 85%

An interesting question is the trend of the oxidation over the three hours. Here the graph of the data is interesting. The blue line is energy from fat and the brown line is energy from carbs. The x-axis is time. Note that as time proceeds Ben is drawing less and less energy from fat and more and more from carbohydrates. The R^2 values show a strong significance.

Ben’s individual Fat Oxidation data is not too far off of the data from the study. The average makes it look as if a person could continue on seemingly forever but Ben’s data shows that is not the case.

Similarly, his carb oxidation rate is very similar to the average since it shows a steady climb up.

It should also be recalled that although fat provides 9 calories per gram and carbohydrates provide 4 calories per gram fat is burned less efficiently for energy – about 10% less efficient than carbohydrates.