October Nutrition Feature: Dietary Fat Intake and the Athlete

October 03, 2012

Fat is a major source of energy in the diet. Dietary fat contains nine calories per gram which is more than two time the calories provided by carbohydrate or protein. Some fat in the diet is essential for proper body function. Fat can also be used as an energy source for muscles during low intensity exercise. This is especially important for endurance athletes. Knowing how much fat and which types of fat to consume is essential for a healthy diet.

All Fats Are NOT Created Equal
Dietary fat is an essential macronutrient which is important for the absorption of fat soluble vitamins A, D, E and K. Fat protects your vital organs and enables you to tolerate exposure to the cold. Fat is also a hunger suppressor and contributes to how “full” you feel after a meal, which can determine how well you stick to a meal plan, and finally fat is an energy reserve. It provides a ready energy source which helps prevent muscle loss while losing weight or exercising.

For optimal health, limiting saturated and trans fats in the diet and replacing them with monounsaturated and polyunsaturated fats is essential. Both a sports diet and a heart healthy diet should limit fat to 20 to 35% of calorie intake.

Saturated fat is found mainly from animal sources of food. These foods include well- marbled meat, poultry skin, bacon, sausage, butter and whole milk products. Saturated fat can raises total blood cholesterol levels and low-density lipoproteins (LDL) cholesterol levels, which will increase your risk for cardiovascular disease. Saturated fat intake may also increase your risk of type 2 diabetes.

Trans fat occurs naturally in some foods, but most trans fats are made during food processing through partial hydrogenation of unsaturated fats. This creates fats that are easier to cook with and less likely to spoil. Trans fats are found in highly processed foods such as cookies, doughnuts and crackers—check your labels. Trans fats can also increase LDL cholesterol and lower healthy high density lipoprotein (HDL) cholesterol.

Monounsaturated fats can improve blood cholesterol levels and may benefit insulin levels and blood sugar control. Monounsaturated fats are found in olive oil, peanut oil, canola oil, avocados, nuts and seeds.

Polyunsaturated fats found mostly in plant based foods and oils can also improve blood cholesterol levels and decrease the risk for type 2 diabetes. Omega 3 fatty acids found in fatty fish such as salmon, haddock and plant sources such as flaxseeds, pumpkin seeds and walnuts, can be especially beneficial in helping prevent heart disease and may also have anti-inflammatory properties. However, the fish highest in omega-3 fatty acids also are the highest in methyl mercury, so limit consumption to 8 oz. of oily fish per week. Vegetable oils such as safflower, corn sunflower and soy are rich in this healthy fat.

Calculating Your Fat Intake
For a healthy diet, intake from fat should be limited to 20 to 35% of calorie intake. If your cholesterol level is high your doctor may recommend a diet that is 20% fat. If you are an active person with low cholesterol you probably don’t need to be as restrictive. To calculate the amount of grams fat per day you need to 1) estimate how many calories you need per day 2) Multiply your total daily calories by 20-35% to determine the number of calories from fat you should consume per day and 3) Divide you fat calories by 9 to determine the grams of fat per day (1 gram of fat is 9 calories). For example, if you were an active women who consumes 2000 calories per day and wanted to limit your fat intake to 25%, you would use the following equation:

0.25 X 2,000 total cal = 500 cal fat 500 cal fat / 9 cal/g = 56 g fat/ day

If you are very active and/or underweight you can use healthy fats to boost your calorie intake. Remember it is important to limit fat intake even if you are eating mainly health fat because it is so calorie dense it can easily increase caloric intake and lead to weight gain.

Fat as an Energy Source during Exercise
One pound of stored fat can provide approximately 3,600 calories of energy. These calories are not readily accessible to athletes performing quick, high intensity exercise such as sprinting or weight lifting. Stored carbohydrate or glycogen can fuel about 2 hours of moderate to high intensity exercise. If glycogen stores are depleted and exercise continues at an intense level, an athlete will not switch to fat stores they will most likely “hit the wall”. Carbohydrate needs to be replenished for exercise to continue. Fat can provide energy during exercise that occurs at a lower intensity. Fat is a great fuel for endurance events, but it is simply not accessible for high intensity exercise. If exercising at a low intensity (or below 50 percent of max heart rate), you have enough stored fat to fuel activity for hours or even days as long as there is sufficient oxygen to allow fat metabolism to occur. Converting stored body fat into energy is a slow process and requires a lot of oxygen so exercise intensity must decrease for this to occur. If you are exercising at a higher intensity eating fat right before or during exercise is not recommended as it takes longer to digest.

References

Academy of Nutrition and Dietetics (2012). Everyday Eating for a Healthier You. Retrieved Sept.20,2012 from http://www.eatright.org/WorkArea/DownloadAsset.aspx?id=6442462534

Clark, Nancy.2008. Nancy Clark’s Sports Nutrition Guidebook. 4th ed. Champaign: Human Kinetics.

Mayo Clinic (2011). Dietary fats: Know which types to choose. Retrieved Sept. 20, 2012 from http://www.mayoclinic.com/health/fat/NU00262/NSECTIONGROUP=2

Quinn, Elizabeth. 2007. Sports Nutrition –How Fat Provides Energy for Exercise. Retrieved Sept. 20,2012 from http://sportsmedicine.about.com/od/sportsnutrition/a/Fat.htm

Rodriguez NR, DiMarco NM, Langley S; American Dietetic Association; Dietitians of Canada; American College of Sports Medicine. Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance. J Am Diet Assoc. 2009 Mar;109(3):509-27.

Kristen Logue RD, LDN

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