In a previous issue of RunMinnesota magazine, which is published by the Minnesota Distance Running Association (full disclosure: I’m on the board), the topic of fat as a fuel for runners came up. The article, written by a dietician from the Mayo Clinic Sports Medicine Clinic in Minneapolis, attacked dietary fat (as is done in many nutrition circles) as having no place in the diet of a runner, or endurance athlete for that matter. Based on the research I’ve seen and my own personal experience seeing fat consumption as beneficial for both health and performance, I wrote a letter to the editor challenging the assertion that dietary fat is really “performance-degrading,” as proclaimed by this sports performance dietician.
Below is the response, including citations for the studies I mention. What are your thoughts on the role of fat in the diet of endurance athletes. Leave a comment below.
The article in the March/April 2015 issue entitled “Building Your Nutrition Base” rightly emphasizes nutrition as the foundation for our running training and racing. However, I found its use of the term “performance-degrading” to characterize dietary saturated fat as out of step with current scientific evidence on nutrition. At submaximal exercise intensities, much of the exercise science research shows enhanced fat burning and endurance after periods of consuming a high-fat diet. For example, a 1994 study among cyclists found that despite a lower muscle glycogen content, those consuming a high-fat diet (70% fat; 7% carbohydrate) were able to sustain moderate intensity exercise until exhaustion lasting almost twice as long as those on a high carbohydrate diet (74% carbohydrate; 12% fat).  More recent research by well-known exercise physiologists Volek, Noakes, and Phinney reinforces these earlier findings with more evidence to support the use of dietary fat as a fuel for endurance exercise. 
One specific sub-set of saturated fat, medium chain triglycerides, are also a readily used fuel by the body that can result in greater energy expenditure. As such, they are being used in weight loss interventions  and have been shown in previous research to enhance endurance. 
Beyond athletic performance, recent research also challenges previously held notions that saturated fat is health-degrading as well. A 2010 review found that “there is no significant evidence for concluding that dietary saturated fat is associated with increased risk of CHD [coronary heart disease] or CVD [cardiovascular disease].  A 2014 study reinforced this finding and further cautioned about the potential adverse health outcomes from replacing dietary saturated fat with dietary carbohydrates. 
As we learn more and more about diet and human performance, we should continue to reassess our firmly held beliefs on the matter, and continue to let science guide our approaches.
 Lambert EV, Speechly DP, Dennis SC, Noakes TD. Enhanced endurance in trained cyclists during moderate intensity exercise following 2 weeks adaptation to a high fat diet. Eur J Appl Physiol Occup Physiol. 1994;69(4):287:293.
 Volek JS, Noakes T, Phinney SD. Rethinking fat as a fuel for endurance exercise. Eur J Sport Sci. 2015;15(1):13-20.
 St-Onge MP, Jones PJ. Physiological effects of medium-chain triglycerides: potential agents in the prevention of obesity. J Nutr. 2002;132(3):329-332.
 Fushiki T, Matsumoto K, Inoue K, Kawada T, Sugimoto E. Swimming endurance capacity of mice is increased by chronic consumption of medium-chain triglycerides. J Nutr. 1995;125(3):531-539.
 Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. Am J Clin Nutr. 2010;91(3):535-546.
 Volk BM, Kunces LJ, Freidenreich DJ, Kupchak BR, Saenz C, et al. Effects of step-wise increases in dietary carbohydrate on circulating saturated fatty acids and palmitoleic acids in adults with metabolic syndrome. PLoS ONE. 2014;9(11): e113605. doi:10.1371/journal.pone.0113605
The article originally appeared in the May/June 2015 issue of RunMinnesota Magazine.