Young Ju, Ph.D.

Fat is one of the macronutrients that provide energy to the body (carbohydrate and protein are the other two). Although carbohydrates are the major energy sources during tennis play, fat is also used as an energy source, especially during longer matches and training sessions.  Fat is a denser calorie source providing 9 calories per gram, whereas carbohydrates and proteins provide 4 calories per gram.  In addition to functioning as an energy source, fat supports structural components such as cell membranes in the body, carries and absorbs fat-soluble vitamins (A, D, E and K), and is involved in numerous physiological processes of the body.

Types of Fat

In the 1970s, a low-fat diet was recommended to lower the risk of heart disease. Since then, research has found that ingesting “healthy” fat and avoiding “bad” fat are more important than eating low-fat.  Fatty acids and glycerol are the basic units of fats.  

The four major dietary fats are as follows (Linus Pauling Institute):

• Saturated fats: beef, pork, poultry, butter, eggs and tropical oils (e.g., coconut, and palm)

• Trans-fats: naturally occurring trans-fats produced in the gut of some animals and foods made from these animals (e.g., milk and meat products) and artificial trans-fats generated in the industrial food process (e.g., fast food, baked goods, fried foods, snacks, and margarine)

• Monounsaturated fats (only one unsaturated chain): olive oil

• Polyunsaturated fats (multiple unsaturated chains): Among polyunsaturated fatty acids, essential fatty acids cannot be synthesized in the body and must be obtained from foods.  There are two classes of essential fatty acids, omega-3 and omega-6 fatty acids.

  • Omega-6: vegetable oils, safflower oil, meat, poultry, and eggs

  • Omega-3: oily fish, krill oil, algae oil, green leafy vegetables, nuts and seeds, canola and soybean oils.  Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are the major end products of omega-3 fatty acids.

Saturated and trans-fats are considered “bad” fats, while monounsaturated and polyunsaturated are considered “healthy.”  The Dietary Guidelines for Americans (2020-2025) recommends limiting (bad) saturated fats to less than 10%, and (bad) trans-fats to less than 1% of daily calories for good health (USDA DGA). For an individual eating 2000 calories a day, this means fewer than 20 calories (or 2.2 grams) of saturated fats, and fewer than 2 calories or (0.2 grams of trans fats).

When and How Much to Take

The Dietary Guidelines for Americans (2020-2025) recommends keeping total fat intake to no more than 25-30% of daily calories (USDA DGA).  The average fat intake level in American adults is higher than the recommendation (34.6 - 35.1% of daily calories) (CDC).

For athletes, the dietary recommendations of fat intake are wider than the general recommendation (20-35% of daily calories).  Fat intake guidelines for tennis players training at a high intensity and for long duration should be no more than ~2 g/kg body weight per day (~140 g/ 70 kg player–154 lbs) (Ranchordas et al., 2013).  Eating a meal containing fat 2-3 hours before and after playing tennis is recommended..

Foods Containing Fat

It is important to consume adequate as well as healthy fat. The best sources of essential fatty acids are “fatty” fishes (salmon, tuna, mackerel), some seeds (flaxseeds, pumpkin seeds, walnuts), and oils (flaxseed oil, soy oil, olive oil).

Fat Supplements

Fat supplements are medical foods formulated for people whose bodies cannot digest certain foods properly and cannot absorb fat.  This includes people with gluten or lactose intolerance or people with unintended weight loss (e.g., HIV/AIDS patients, cancer patients).  A prescription is not required to purchase medical foods.  Fat supplements are made from formulated fatty acids, often from safflower oil. Therefore, an individual who is allergic to safflower oil should not use a fat supplement.  

Although omega-3 fatty acids, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have attracted more attention in sports nutrition, there is no specific study for tennis players. Studies have reported that omega-3 fatty acid supplementation (4 grams per day) may provide anti-inflammatory properties and be beneficial to the injured athlete (Joyce 2015; Smith et al., 2011a and 2011b).  In athletic performance, few studies of EPA/DHA supplementation are available; findings from those studies suggest that EPA/DHA supplementation may improve endurance capacity and delay onset of muscle soreness (Thielecke and Blannin, 2020).

Potential Adverse Effects

It is rare for healthy people to become fat deficient.  However, people with some health conditions, such as an eating disorder, colectomy, inflammatory bowel disease, cystic fibrosis, pancreatic dysfunction, can develop fat deficiency. An extremely low-fat diet or too little fat intake can lead to organ damage, vitamin deficiencies, dermatitis, osteoarthritis, hair loss, and hormonal imbalance, and it may decrease athletic performance, endurance, and recovery. 

Too much fat intake can lead to weight gain causing chronic knee problems, joint pain, and/or impaired performance and recovery.  High-fat intake is associated with increased cholesterol levels, blood pressure, inflammation, and other metabolic conditions.

Who Should Be Cautious with High-Fats?

People with diabetes, heart disease, certain types of cancer (including breast cancer, colon cancer), and/or overweight/obesity can be affected by the types and amount of fats in their diet. Taking healthy fats in the recommended amounts could help manage these health conditions.

People with certain health conditions such as diabetes, epilepsy, or Alzheimer’s disease who use a ketogenic diet should monitor blood cholesterol levels and blood pressure. A  ketogenic diet is characterized by lower carbohydrates (5 - 10% of daily calories) and higher fats (55 – 60%) and proteins (30 – 35%) to compensate for a glucose (a major fuel in the brain) deficit with ketone bodies (fatty acid metabolites) in the brain. 

REFERENCES

Joyce D. Sports Injury Prevention and Rehabilitation. Routledge; New York, NY, USA: 2015.

 Ranchordas et al. Nutrition for tennis: practical recommendations. J Sports Sci & Med 2013, 12(2): 211.

 Smith et al. Omega-3 polyunsaturated fatty acids augment the muscle protein anabolic response to hyperinsulinaemia–hyperaminoacidaemia in healthy young and middle-aged men and women. Clin. Sci. 2011a, 21:267.

 Smith et al. Dietary omega-3 fatty acid supplementation increases the rate of muscle protein synthesis in older adults: A randomized controlled trial. Am. J. Clin. Nutr. 2011b, 3:402.

 Thielecke F and Blannin A. Omega-3 Fatty Acids for Sport Performance-Are They Equally Beneficial for Athletes and Amateurs? A Narrative Review. Nutrients 2020, 12(12):3712

 Centers for Disease control and Prevention. National Center for Health Statistics: Diet/Nutrition https://www.cdc.gov/nchs/fastats/diet.htm

 Linus Pauling Institute. Micronutrient Information Center: Essential Fatty Acids https://lpi.oregonstate.edu/mic/other-nutrients/essential-fatty-acids 

 USDA Dietary Guidelines for Americans 2020-2025 https://www.dietaryguidelines.gov/sites/default/files/2020-12/Dietary_Guidelines_for_Americans_2020-2025.pdf

 USDA National Nutrient Database for Standard Reference Legacy (2018) Nutrients: Fatty acids, total saturated  https://www.nal.usda.gov/legacy/sites/default/files/sat_fat.pdf

People with any other health problems should talk to their healthcare providers about fat intake. As always this information is provided for your reference and you use at your own risk; you should rely on your medical professional for medical advice.