Fat in the Diet of the Ultra-Endurance Athlete: Fueling for the Distance
Fats, or lipids, are important components of plant, animal and microbial cell membranes. Fat is a major energy source, with 1 gram of fat yielding 9 kcalories, as compared to 1 gram of either protein or carbohydrate, which yield 4 kcal per gram. Only 1 level 5 ml measure (1 level tsp) yields 45 kcal! Being so energy-dense, fat is the most efficient way for the human body to store energy. One pound of fat tissue (adipose) yields a whopping 3500 kcal!
Fat also helps maintain body temperature and protects the vital organs from trauma. Fat aids in the delivery of fat-soluble vitamins and carotenoids, contributes to the taste and palatability of food and influences the texture of foods. We are genetically predisposed to loving it! For many, over-consumption leads to obesity when activity does not match intake.
Endurance athletes use the aerobic energy system with brief, intermittent involvement of anaerobic energy systems. Exercise intensities may range between 50% and 90% maximum oxygen consumption (VO2MAX ) for events lasting 4-24 hours, with total energy expenditures ranging between 5,000 and 10,000 kcal per day.
In an endurance event such as an ultra-run, the exercise intensity averages 65% VO2MAX and lipids (fats) provide the most fuel. Even so, exercise can only be maintained for prolonged periods without the onset of fatigue is sufficient carbohydrate is available. If the intensity of the exercise is increased, or if the body is stressed for any reason (for example: wind, temperature, or pain), carbohydrate becomes the primary fuel source.
How much Fat is Enough?
Distance runners have been reported to consume between 27-35% of the total energy as fat. Compare this to non-endurance, more appearance-oriented sports like gymnastics or figure skating, where fat in the diet may range from 15-31%. Overly restricting fat in the diet of an endurance athlete could cause problems with temperature regulation, hormone balance and protection against trauma.
30% of energy from fat in the diet is still considered a relatively low fat diet. Expressed in amount per kilogram body weight, this should equal 0.8- 1.0 gram fat per kilogram body weight. For a 65 kg women, this equates to a requirement of 52-65 grams of fat per day. To get an idea what this might mean in real food, refer to the table below:
Fat Content of Typical Foods
Food |
Fat (grams) |
Fat/ Typical \Portion |
30g (1 oz) lean meat, fish, poutry, 1 whole egg |
3-4 |
3-16 |
30 g (1 oz) high fat meat, fish, poultry |
7-8 |
7-24 |
30 g (1 oz) cheddar |
8 |
8-16 |
30 g egg whites/whey |
0 |
0 |
15 ml (1 Tbsp) peanut/almond butter |
8 |
18 |
250 ml (8oz) skim milk |
0 |
0 |
250 ml (8oz) 3.5% milk |
8 |
8, 16 or more |
5 ml (1 tsp) butter, margarine, oil, mayonnaise |
5 |
10+ |
1 slice bread |
1-2 |
2-4 |
Most fruit, vegetables |
0 |
0 |
30 potato chips |
22-30 |
25 |
1 square chocolate |
4 |
16 |
1 donut |
8-27 |
15 |
Small hamburger |
11 |
11 |
Triple burger with cheese |
83 |
83 |
Consider the Quality of the Fat in the Diet
To maintain heart and arterial health, and to avoid a multitude of major diseases, including cancer and dementia, it is important to emphasize eating healthy fats, like olive, canola, flax oils, soft non-hydrogenated margarines, nuts, seeds, fatty fish and lean meats. Minimize intake of saturated fats and trans-fat containing foods (store-bought baked goods, deep-fried foods and snacks, fatty meats and full fat dairy products.)
Effect of Fat on Stomach Emptying
When any particular meal or snack is high in fat, the valve at the bottom of the stomach, known as the pyloric sphincter, tends to narrow, resulting in slowing the emptying of the stomach contents into the intestine. When at rest, this may or may not cause gastric upset, depending on the person. (Think of the “after-turkey dinner feeling” or a heaviness or “thud” in your gut.) When physically active, the body prefers to divert most of its work to the moving limbs, causing the gut to slow down more. Most athletes have learned to avoid any high fat foods prior to or during any practice or event to avoid feeling nauseous or weighed down. If you must indulge in some fatty delicacy, but sure it is AFTER your workout.
References
Kreider, RB. Physiological considerations of ultraendurance performance. Int J Sport Nutr. 1991;1:3 3-27
Acheton J, Gleeson M,Jeukendrup AE. Determination of the exercise intensity that elicits maximal fat oxidation. Med Sci Sport Exerc 2002;34:92-97
Laursen PB, Rhodes, EC. Physiological analysis of a high-intensity ultraendurance event. J. Strength Cond Res. 1999;21:26-38
Williams C. Dietary macro-and micronutient requirements of endurance athletes. Proc Nutr Soc. 1998;57:1-8.
