Tag Archives: ultrarunning

High fat diets and ultrarunning

Under normal conditions of exercise the body has two main sources of fuel: fat and carbohydrate (CHO).  The According to Jeukendrup 2003, the body has roughly 2000 kcal of stored CHO, stored primarily as muscle glycogen.  If we assume that an average person would expend ~100 kcal per mile of running, then this would translate to ~20 miles of running(Jeukendrup, 2003).  In contrast, the Jeukendrup 2003 reports that the human body stores roughly 106,000 kcal of fat, primarily in adipocytes (100,000 kcal) and secondarily as intramuscular triacylglyceride (2600 kcal) (Jeukendrup, 2003).  Theoretically, there are several possible benefits to increasing reliance on fat oxidation.  As previous research has shown that glycogen availability may impact force generation by modulating sarcoplasmic reticulum (SR) calcium release (Ørtenblad, Nielsen, Saltin, & Holmberg, 2011), sparing muscle glycogen by oxidizing more fat may preserve force generation. In order to be metabolized, fat is mobilized from triglyceride storage and delivered to the mitochondria as free fatty acids (Horowitz & Klein, 2000).  Fatty acids are then broken into 2 carbon fragments in the form of acylCoa.  During this process one FADH and one NADH are generated, but no direct rephosphorylation of ADP to ATP occurs.  Unlike oxidation of glucose, fat oxidation requires more flux through the oxidative pathways since generation of ATP is nearly exclusively through the electron transport chain (ETC) (Gropper & Smith, 2012).  Since there increased flux through ETC there may be a training effect to increasing reliance on fat as a fuel source (Miller, Bryce, & Conlee, 1983; Simi, Sempore, Mayet, & Favier, 1991).

Several studies on rats have provided encouraging data that high fat diets may improve endurance capacity through stimulating increases in oxidative enzymes and preservation of muscle glycogen stores (Conlee et al., 1990; Miller et al., 1983; Simi et al., 1991).  Miller et al., 1983 showed that a high fat diet reduced muscle glycogen and liver stores, but also improved exercise capacity and oxidative enzymes (Miller et al., 1983).  Simi et al., 1991 provided evidence that while training may blunt this effect, there is still an effect on oxidative capacity for a high fat diet after training in rats.  However, it is possible this effect could disappear if the training stimulus were high enough since the training stimulus used was quite small (Simi et al., 1991).  Conlee et al., 1990 may suggest there is added benefit to fat adapting a rat and then transiently increasing CHO prior to exercise (Conlee et al., 1990).

It is important to understand that while these results are encouraging, human studies have had less positive results (Horvath, Eagen, Fisher, Leddy, & Pendergast, 2000; Rowlands & Hopkins, 2002; Vogt et al., 2003).  This may be in part due to the large variation in diets deemed high fat in human studies.  The animal studies tended to have fat intakes around 70% of the diet, whereas high fat diets in human studies have ranged from 44-70%.  It appears there may be two defined diets based on the literature.  The first diet deemed high fat is based on increasing fat intake beyond the recommended 20-35% of calories (“Nutrition and Athletic Performance,” 2009).  These diets tend to have a higher proportion of fat, but maintain a substantial contribution from carbohydrates (Horvath et al., 2000; Rowlands & Hopkins, 2002; Vogt et al., 2003).  The other version of the high fat diet is additionally very low carbohydrate (Goedecke et al., 1999; Lambert, Speechly, Dennis, & Noakes, 1994).  Such a large range of diets classified as high fat may be partly responsible for the mixed results.  In support of this, Lambert et al., 1994 found that a diet of 70% fat significantly improved time to exhaustion at 60% of VO2max.  However, time to exhaustion at 90% VO2max and CHO oxidation rates at high intensity were unaltered (Lambert et al., 1994).  Goedecke et al 1999 used a high fat diet, 69 ± 1% fat, for 15 days (Goedecke et al., 1999).  Carnitine acyl transferase activity was significantly increased within 5-10 days of being fed a high fat diet.  However, 40 km cycling time trial performance was not significantly different compared with a high carbohydrate diet.  Taken together, it appears that a high fat, low carbohydrate diet may have beneficial effects at moderate intensity activities, but when intensity is increased beyond a certain threshold, the working muscles will still shift to burning almost exclusively carbohydrate.  After this shift occurs, there is likely no performance benefit to a high fat diet.

Early studies on high fat diets focused on the metabolic consequences of such diets which were shown to induce obesity in animal models (Mašek & Fabry, 1959).  In fact, a number of studies have shown that high fat diets can induce metabolic syndrome and insulin resistance (Ikemoto et al., 1996; Oakes, Cooney, Camilleri, Chisholm, & Kraegen, 1997; Todoric et al., 2006; Tschöp & Heiman, 2001).  However, it should be noted that the type of fat used in the diet can have an impact on this outcome.  Particularly, Ikemoto et al. 1996 found there was a positive association between linoleic acid intake and plasma glucose, and that a diet high in fish oil actually had beneficial effects on body weight and glucose uptake.  Other studies have suggested there is a beneficial effect on health for diets high in fish oil (Buettner et al., 2006).  It appears there may be a gap in the literature on the long term consequences of high fat diets in combination with endurance exercise.  In light of this, it would be prudent to recommend athletes attempting to alter substrate utilization through a high fat diet should consume most of their fats from sources shown to not adversely affect glucose uptake.

Literature on high fat diets and exercise performance that account for types of fat seem to be scarce.  However, there have been a number of experiments examining medium chain fatty acids as a potential energy source during exercise.  Medium chain fatty acids are described as fatty acids with 6-10 carbons that readily cross the mitochondrial membrane where medium chain acyl CoA synthases activate them before they are oxidized (Marten, Pfeuffer, & Schrezenmeir, 2006).  The rationale would be to supplement with the medium chain fatty acids just prior to or during exercise to provide an energy source during exercise (Angus, Hargreaves, Dancey, & Febbraio, 2000; Jeukendrup, Saris, Schrauwen, Brouns, & Wagenmakers, 1995).  However, as pointed out by Jeukendrup et al. 1995, the GI tract has a low tolerance for medium chain fatty acids during exercise, which may limit its usefulness as an ergogenic aid.

It is currently unclear why someone might recommend a high fat diet for strength performance.  Anecdotally, numerous books promote “paleo” diets which tend to be low carbohydrate, higher fat, for numerous athletic populations (Burnett, 2012; Outram, 2014; Smith, 2012).  Many of these books claim that humans evolved to eat only meat based on little or no actual research.  However, some studies have attempted to examine early human diets, but found that early humans likely ate a mixed diet with slightly increased protein and decreased fat intake (Nestle, 2000), while other studies contradict this finding suggesting diets were high in fat and low to moderate in carbohydrate (Eaton & Eaton Iii, 2000).  Studies on modern indigenous tribes suggest there may also be a larger role for dietary fiber for such populations (Johns, Nagarajan, Parkipuny, & Jones, 2000).  It may be that early humans had a large range of diets depending upon food availability and regional culture.  It should also be noted that it is currently unclear whether early humans were any healthier due to their diets (Nestle, 2000).  One study suggests that the stereotypical “caveman” diet would be lethal to pregnant women and their fetuses (Hockett, 2012), suggesting that these diets may differ from popular conception.  It appears there is very little literature on using a high fat diet to improve performance for strength athletes.  However, high fat meals have been shown to reduce total and free testosterone (Cano et al., 2008; Volek, Love, Avery, Sharman, & Kraemer, 2001), but it is unclear whether these reductions in androgens would be large enough to affect adaptation to strength training.




Angus, D. J., Hargreaves, M., Dancey, J., & Febbraio, M. A. (2000). Effect of carbohydrate or carbohydrate plus medium-chain triglyceride ingestion on cycling time trial performance. J Appl Physiol (1985), 88(1), 113-119.

Buettner, R., Parhofer, K., Woenckhaus, M., Wrede, C., Kunz-Schughart, L., Schölmerich, J., & Bollheimer, L. (2006). Defining high-fat-diet rat models: metabolic and molecular effects of different fat types. Journal of molecular endocrinology, 36(3), 485-501.

Burnett, K. (2012). The Paleo Diet: Fact or Fiction?

Cano, P., Jiménez-Ortega, V., Larrad, Á., Toso, C. F. R., Cardinali, D. P., & Esquifino, A. I. (2008). Effect of a high-fat diet on 24-h pattern of circulating levels of prolactin, luteinizing hormone, testosterone, corticosterone, thyroid-stimulating hormone and glucose, and pineal melatonin content, in rats. Endocrine, 33(2), 118-125.

Conlee, R. K., Hammer, R. L., Winder, W. W., Bracken, M. L., Nelson, A. G., & Barnett, D. W. (1990). Glycogen repletion and exercise endurance in rats adapted to a high fat diet. Metabolism, 39(3), 289-294.

Eaton, S. B., & Eaton Iii, S. B. (2000). Paleolithic vs. modern diets–slected pathophysiological implications. European journal of nutrition, 39(2), 67-70.

Goedecke, J. H., Christie, C., Wilson, G., Dennis, S. C., Noakes, T. D., Hopkins, W. G., & Lambert, E. V. (1999). Metabolic adaptations to a high-fat diet in endurance cyclists. Metabolism, 48(12), 1509-1517.

Gropper, S., & Smith, J. (2012). Advanced nutrition and human metabolism: Cengage Learning.

Hockett, B. (2012). The consequences of Middle Paleolithic diets on pregnant Neanderthal women. Quaternary International, 264, 78-82.

Horowitz, J. F., & Klein, S. (2000). Lipid metabolism during endurance exercise. The American journal of clinical nutrition, 72(2), 558s-563s.

Horvath, P. J., Eagen, C. K., Fisher, N. M., Leddy, J. J., & Pendergast, D. R. (2000). The effects of varying dietary fat on performance and metabolism in trained male and female runners. Journal of the American College of Nutrition, 19(1), 52-60.

Ikemoto, S., Takahashi, M., Tsunoda, N., Maruyama, K., Itakura, H., & Ezaki, O. (1996). High-fat diet-induced hyperglycemia and obesity in mice: differential effects of dietary oils. Metabolism, 45(12), 1539-1546.

Jeukendrup, A. E. (2003). High-carbohydrate versus high-fat diets in endurance sports. SCHWEIZERISCHE ZEITSCHRIFT FUR SPORTMEDIZIN UND SPORTTRAUMATOLOGIE, 51(1), 17-24.

Jeukendrup, A. E., Saris, W., Schrauwen, P., Brouns, F., & Wagenmakers, A. J. (1995). Metabolic availability of medium-chain triglycerides coingested with carbohydrates during prolonged exercise. J Appl Physiol (1985), 79(3), 756-762.

Johns, T., Nagarajan, M., Parkipuny, M. L., & Jones, P. J. (2000). Maasai Gummivory: Implications for Paleolithic Diets and Contemporary Health1. Current anthropology, 41(3), 454-459.

Lambert, E. V., Speechly, D. P., Dennis, S. C., & Noakes, T. D. (1994). Enhanced endurance in trained cyclists during moderate intensity exercise following 2 weeks adaptation to a high fat diet. European Journal of Applied Physiology and Occupational Physiology, 69(4), 287-293.

Marten, B., Pfeuffer, M., & Schrezenmeir, J. (2006). Medium-chain triglycerides. International Dairy Journal, 16(11), 1374-1382.

Mašek, J., & Fabry, P. (1959). High-fat diet and the development of obesity in albino rats. Experientia, 15(11), 444-445.

Miller, W. C., Bryce, G., & Conlee, R. (1983). Adaptations to a high fat diet which increase exercise endurance in male rats. Am Physiological Soc.

Nestle, M. (2000). Paleolithic diets: a sceptical view. Nutrition Bulletin, 25(1), 43-47.

Nutrition and Athletic Performance. (2009). Medicine & Science in Sports & Exercise, 41(3), 709-731 710.1249/MSS.1240b1013e31890eb31886.

Oakes, N. D., Cooney, G. J., Camilleri, S., Chisholm, D. J., & Kraegen, E. W. (1997). Mechanisms of liver and muscle insulin resistance induced by chronic high-fat feeding. Diabetes, 46(11), 1768-1774.

  • rtenblad, N., Nielsen, J., Saltin, B., & Holmberg, H. C. (2011). Role of glycogen availability in sarcoplasmic reticulum Ca2+ kinetics in human skeletal muscle. The Journal of Physiology, 589(3), 711-725.

Outram, J. (2014). Paleo for Beginners: All about the Paleo Diet: How to Get Healthy & Lose Weight: Speedy Publishing LLC.

Rowlands, D. S., & Hopkins, W. G. (2002). Effects of high-fat and high-carbohydrate diets on metabolism and performance in cycling. Metabolism, 51(6), 678-690.

Simi, B., Sempore, B., Mayet, M., & Favier, R. J. (1991). Additive effects of training and high-fat diet on energy metabolism during exercise. J Appl Physiol, 71(1), 197-203.

Smith, R. (2012). Paleo Diet Guidelines & Procedures: Caveman Diet: ShirdInc.

Todoric, J., Löffler, M., Huber, J., Bilban, M., Reimers, M., Kadl, A., . . . Stulnig, T. (2006). Adipose tissue inflammation induced by high-fat diet in obese diabetic mice is prevented by n− 3 polyunsaturated fatty acids. Diabetologia, 49(9), 2109-2119.

Tschöp, M., & Heiman, M. L. (2001). Rodent obesity models: an overview. Experimental and clinical endocrinology & diabetes, 109(06), 307-319.

Vogt, M., Puntschart, A., Howald, H., Mueller, B., Mannhart, C., Gfeller-Tuescher, L., . . . Hoppeler, H. (2003). Effects of dietary fat on muscle substrates, metabolism, and performance in athletes. Med Sci Sports Exerc, 35(6), 952-960.

Volek, J. S., Love, D. M., Avery, N. G., Sharman, M., & Kraemer, W. J. (2001). Effects of a high-fat diet on postabsorptive and postprandial testosterone responses to a fat-rich meal. Metabolism, 50(11), 1351-1355.


Why would someone want to run 100 miles

Just about every time I tell someone that I run 100 mile races I get reactions that starts with shock and surprise, followed by the universal question “why would someone want to do that?”  It’s a question we all struggle to answer in words because the it’s so glaring obvious to us.  I find myself stammering out a few incoherent sentences about enjoyment or some other aspect, but to me, I find it more incomprehensible as why you wouldn’t want to run 100 miles.  The idea of not wanting to do this is as foreign to me as the thought of wanting to spend a Saturday in bed or enjoying a lifetime docudrama on a dad’s misadventures at the grocery store.  To me, what I do is the natural expression of who I am.  I want to spend all day in nature, hanging out with these incredible people, drinking good beer, and yes running.  So in some sense running a 100 mile race is no different than any other activity that people enjoy.  However, I feel there are some things we can pull out that attract us to this idea.

First and foremost, there is something about the distance which captivates my imagination.  100 miles!  It sounds impossible.  The distance is extreme enough that the first time we hear about it, we cannot fathom it.  It’s the unknown.  It’s like someone 300 years ago hearing about this exotic land across the sea and wanting to experience it firsthand.  With so few real frontiers available, the modern explorer may turn inward and desire to explore their own limits.  How will I feel at 60 or 70 miles?  What about the finish line?  What is it like to have this experience?

Second, I think most people running these races are in search of something unique.  I suspect a lot of my ultrarunning friends may be like me in that we search out the strange and unique things.  I cannot be interested in “normal” things.  My wife says that I have to find the strangest thing to be obsessed with.  Due to the strenuous nature of running 100 miles, it is still fortunately considered strange.  I hope we never lose that.

Third, the ultrarunning community provides us with a tribe.  We all have similar experiences that most people cannot relate to.  Through this shared experience we have a group to identify with.  I think it may be a reaction against modern culture which tends to promote sameness.  We watch the same tv programs, go to the same schools with the same curriculum, so that we can all be part of one giant group called “americans.”  But, it’s all cold and impersonal.  We may not really feel that we fit into the national culture, so we retreat to our mountain trails to be with people we share a deeper connection to.  People we have bled with or shed tears with, of joy and pain.

Lastly, I think running 100 miles allows us to have an emotional journey.  We get to experience the full spectrum of human emotions in one day.  It is a spiritual and emotional quest of personal understanding.  One I hope you as my reader get to one day experience for yourself.

Comparison of hydration options

If you are new to the sport of ultrarunning, you will at some point be assaulted by the variety of hydration options out there.  Regardless of the plethora of choices, there are some basic categories, and these categories tend to encompass a common set of positive and negative features.  First, we could break things down by bottles vs bladders.  Bottles have the advantage of being easily trackable throughout a race because you can visually see how much you’re drinking.  They are also cheap and easy to clean.  Many companies have tried to develop their own “ideal” bottle, but I find my favorite bottle is the Gatorade Sports bottle with the twist top.  It’s large enough that I usually need only one, and I can wrap my headlamp around it.  Also, due to the disposable nature I can just recycle it after the race instead of finding it months later stashed in a bag of gear covered in mildew.

The obvious advantage of a bladder is the convenience of being able to sip through a straw.  This is also a disadvantage though since you may tend to over or under consume fluids this way.  I like to be anal about tracking my fluid consumption and matching sodium intake.  You can buy an inline meter for a bladder to tell you how much fluid you have consumed, like the one below.

However, there are numerous other reasons I personally dislike bladders.  First would be the price.  These are just some samples of replacement bladders, which generally cost ~20 dollars.  

For that same price I could get 10 bottles and have my imaginary crew keep a stock of filled bottles.  Another major disadvantage is the durability.  When I used bladders, I generally had to buy a new bladder every month due to either mold or tears that would develop around the closure, or on the bladder itself.  If you are a poor PhD student like me, this becomes unsustainable. I would say though that certain races may provide few opportunities to refill your fluid and a bladder does allow you to carry more fluid usually.

The other way we could break things down by is belts, packs/vests or handhelds.  A lot of people love handhelds, but personally, I really don’t want to have anything heavy in my hand because it would fatigue my shoulder muscles.  This is especially important for my as I have shoulder problems.  That said, some people swear by them and love the shock absorption from falling on the bottle instead of their hands.  I personally use belts, but they also have a drawback in that they either flop around or you cinch them so tight they press on your GI tract which can be uncomfortable.  I own several running belts and I can tell you the double bottle belts are terrible unless you just need a lot of fluid.  The double bottle belts become uneven after a couple sips and flop badly.  Not to mention the extra weight is uncomfortable on the GI tract.  I should also say, if you’re running 50 or 100 miles, you probably need some storage space on whichever option you choose.  For this reason I use nathan single bottle belt with storage shown below.

Despite all the drawbacks of belts, I still prefer them for two reasons: they are cheap, and they absorb less heat than the vests.  I’ve used vests, and they are convenient, but since I prefer hot races, I don’t want something sitting against my back holding in heat.  Also, nearly all the options have a bladder.  Despite this, if I were to run a long race without support I would prefer a vest since they usually have the most storage space.  Although I might ditch the bladder or use it to refill bottles.  And if I had the money this is the vest I would buy.

I hope this helps you in your endeavor to find the right hydration system for you.