Fat as an Energy Fuel Source for Runners

Using fat as a fuel source provides the body with an abundant energy source. Since the human body can store unlimited amounts of fat and only a limited amount of carbohydrate, fat provides an individual with plenty of energy when used as a fuel source! A gram of fat provides the body with two times as much energy as a gram of carbohydrate. When ingested a banana (carb source) provides enough fuel to run a mile where as a tablespoon of olive oil (fat source) provides the same amount of fuel and energy to be used by the body.

Fatty acids aka triglycerides are the primary type of fat used by muscle cells to create the energy needed for running. Fatty acids are stored in the muscles, fat cells, and other tissues of the body. Since fat is basically an unlimited fuel source for runners, and based off of my last article on training in a low glycogen state (carb depleted) - http://www.runwithmemeghan.blogspot.com/2014/05/training-with-low-glycogen-levels-is.html - runners should adjust there nutrition and training to produce less reliance on carbohydrates for energy and promote greater fat usage during running. This is true, but how does it affect your training?

Carbohydrates and fats are made up of the same 3 elements: carbon, oxygen, and hydrogen, but the ratio to carbon and oxygen is much greater in fats. Since fat has a higher ration of carbon to oxygen compared to carbohydrates, the use of fat instead of carbohydrate as a primary fuel source during running raises the oxygen consumption rate associated with particular intensities. With this said, the chosen velocity and intensity is carried out at a higher percentage of VO2max. Since perceived effort and VO2max are fairly tightly linked, the intensity of the training will feel much more difficult to sustain when fat is a primary fuel source of energy even though total fuel availability with fat is greater than carbohydrate.

Using fats vs carbohydrates as a fuel source is influenced by a number of factors, including nutrition, running intensity, and the duration of the work out. Balancing your nutrition with your training intensity and duration is important to fuel your body for your work outs. This will vary from person to person based of those factors so it is important to incorporate nutrition along with your training program.

Feel free to post any comments or email me with additional questions!

Happy Fat Fueled Running :)