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Fat & Endurance Athletes

posted Jan 15, 2013, 2:27 PM by Stephanie Violett   [ updated Apr 5, 2013, 8:01 AM ]

Why is fat important for endurance athletes?


         A healthy diet includes adequate amounts of carbohydrates, fats, and protein. Many athletes think that fat is unhealthy, but fat is important for athletic performance and optimal health. Fat provides the essential fatty acids, omega 3 and 6, as well as the fat soluble vitamins, A, D, E, and K, which are important for many metabolic and regulatory processes in the body. Fat is also a component of cell membranes and plays a structural role in the brain and spinal cord. Dietary fat is essential for the body to function and without a healthy body, athletic performance will undoubtedly be impaired.

         In terms of athletic performance, fat is one of the primary fuels used during exercise. One gram of fat yields twice as much energy (9kcal/g) as carbohydrate (4kcal/g), thus when fats are broken down for energy they can fuel the body for a much longer duration. One training adaptation to endurance exercise is enhanced fat utilization, increasing the energy supply during exercise. Another benefit of using fat during exercise is that the body has limited stores of glucose. Once glycogen stores are depleted, fatigue rapidly sets in and performance is negatively affected. Thus, greater reliance on fat during endurance exercise can delay fatigue and also increase exercise duration.


How much fat should I consume? And what type?


         An endurance athlete should aim to consume 20-35% of total energy intake from fat, with the majority coming from monounsaturated and polyunsaturated sources. Some examples of foods that are high in unsaturated fats include olive oil, nuts, avocados, flaxseed, and salmon. Fats should be consumed as part of a well-balanced diet, in meals surrounding exercise sessions. For most endurance events, there is no need to consume fat during exercise. This may not be true with ultra-endurance events (look for a future post on this topic), but for anything less than a few hours carbohydrate intake is recommended. Following exercise, the addition of fat and protein along with carbohydrate can be beneficial for recovery from exercise.


         As with any nutrient, it’s important to consume fat in moderation. Fats are crucial for health and athletic performance, but too much fat can be unhealthy. Most athletes report consuming approximately 30% of total calories from fat, but this number can fluctuate depending on the athlete and the sport. Some of the new diet trends right now include consuming a low carbohydrate diet, which is automatically higher in fat and protein. Besides performance consequences associated with inadequate carbohydrate intake (see my last post), no performance benefits have been found following a high fat intake.  The hypothesis behind the high fat intake before and during exercise is that greater fat availability will spare glycogen and enhance time to fatigue. Since more energy is available (fat yields much more energy than carbohydrate) endurance performance might improve. Many studies have investigated this hypothesis and found that there are no performance benefits with fat intake prior to or during exercise. The rate-limiting step for fatty acid use by the body is not the availability of fats. Thus, consuming fat above what is needed by the body will not further improve endurance performance. On the flip side, athletes who consume too little fat also have no further athletic advantage, and may be putting their health at risk. When fat intake drops below 15% of total energy intake, an athlete will not be getting enough fat for optimal health and athletic performance.

         Determining fat needs can be tricky, especially since the guidelines of 20-35% of total calories can be difficult to quantify. To determine ideal fat intake, it’s best to start with carbohydrate and protein needs and work backwards. An endurance athlete needs approximately 5-7g/kg (females) or 6-10g/kg (males) of carbohydrate and 1.2-1.7g/kg of protein per day. Once the ideal carbohydrate and protein intakes are selected, then the % of total calories consumed can be estimated and fat needs determined. For most athletes, this works out to a fat intake around 1-2g/kg per day.