Sports Medicine Series with Dr. Cahill: The Tie Between Diet and Sports


Whether you’re an all-star athlete striving for a personal best in your sport or a weekend warrior trying to get fit, your diet plays a starring role in how well you perform and the results you can expect to achieve. On the other hand, a poor diet can cancel out the benefits of your exercise program if you eat the wrong foods at the wrong time.

Your nutritional needs will vary according to several factors, including:

  • The type of activity or sport
  • The amount of training it requires
  • The amount of time you spend training

“Your diet gives you the fuel for your chosen activity,” says Dr. Ronan Cahill, a Sports Medicine Physician at Swedish. “You have to have enough food in the right proportions.” 

That sounds simple enough, but what does it really mean?

Here’s a look at the foods you need to achieve peak performance no matter what type of physical activity you enjoy.


Despite the popularity of low- or no-carb diets, athletes need complex carbohydrates for energy, especially for bursts of intense activity. Carbohydrates are converted into glucose (blood sugar), which is used to supply energy throughout your body. Complex carbohydrates found in pasta, whole grain breads, and rice are low in fat and provide fiber, energy and vitamins. Simple sugars like those found in soft drinks, candy and processed foods do not provide the nutrition you need during exercise or athletic activity.

A poor diet can cancel out the benefits of your exercise program if you eat the wrong foods at the wrong time.

“Complex carbohydrates help you perform better and recover faster,” says Dr. Cahill.

  • Eat carbs before exercise if you will be active for more than an hour
  • Eat carbs during exercise if you will be doing more than an hour of intense activity
  • Eat carbs after exercise to rebuild your energy stores


Your body uses protein to repair tissues and aid muscle growth. You do not need to significantly increase your protein intake to see results.

  • Significant muscle growth requires regular training and commitment, not excessive amounts of protein
  • Too much protein may actually harm rather than help your body, resulting in calcium loss, kidney problems and dehydration
  • Good sources of protein include lean meats and poultry, eggs, nuts, beans, broccoli, cauliflower, peas, tofu, legumes and dairy products


Fat sometimes gets a bad rap but some fats are actually good for you. Fat gives you energy and helps your body absorb certain vitamins.

“Fat helps your body’s processes work together,” said Dr. Cahill. “It helps endurance and long-term activity.”

  • Choose unsaturated fats found in fish, nuts, seeds, and vegetable oils for healthier results
  • Limit saturated and trans fats like butter or partially hydrogenated oils
  • Fats can slow digestion so avoid eating them right before rigorous athletic activity

Water and other fluids

Water is just as important to your workout as food. It regulates your body temperature, keeps you hydrated, and replaces any fluids you lose during activity. Water is the ideal drink but sports drinks can also be beneficial when you’re active for longer than 90 minutes because they replace electrolytes and carbohydrates to give you an energy boost.

Water is just as important to your workout as food.

The actual amount of fluid you need depends on several factors like your activity level and the day’s temperature. If your urine is fairly clear, it is a good sign you are getting enough to drink.

  • Drink about two cups of water (16 ounces) two hours before your activity begins
  • Drink a small amount of water or sports drink every 20-30 minutes during activity – or when you feel thirsty

Find a doctor

At Swedish, our sports medicine specialists are fellowship trained in physical medicine and rehabilitation. Their focus is helping you stay active and fit. Find a doctor you can trust in our provider directory.

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About the Author

Whether you're interested in physical fitness, an athlete looking for performance tips, or it's time for a full or partial replacement of knees, shoulders or hips, the Swedish Orthopedics and Sports Medicine Team is committed to providing you with expert advice on how to prevent injury, plan for physical activity and recover from orthopedic procedures. Our mission is to help you live the active lifestyle you want.

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