There are few things in life that seem to confuse people more than nutrition. How many calories should I be eating? How much protein do I need? Should my diet be high carb or high fat? Nutrition for athletes becomes even more complicated since what an athlete eats has a big effect on overall performance. Hopefully this blog post can help clear up some of the confusion when it comes to nutrition for athletes.
The repair and growth of muscle does not occur while a person exercises, the process actually begins in the post-exercise period. After you workout, your body attempts to repair or replace muscle fibres that have been damaged by the exercise session. The raw materials for this repair are supplied by dietary protein. To build muscle, the rate of protein synthesis must be larger than the rate of protein breakdown. In simpler terms, an athlete needs to supply the raw materials to facilitate muscle growth and strength increases. The recommended dietary intake for sedentary adults is .8 grams of protein per kilogram of bodyweight (Health Canada, 2005). This translates to 56 grams of protein for males and 46 grams of protein for females. One of the foremost authorities on protein consumption, Dr. Stuart Phillips from McMaster University, reports the optimal protein consumption for athletes trying to recover from hard exercise sessions to be double the RDI at 1.6-1.8 g/kg/d (Morton et al., 2015). An example of this would be that the protein consumption for a 200 pound male would range between 146 to 164 grams of protein per day.
Once protein needs are met, the next requirement is energy supply. The body’s preferred fuel source is glycogen, which is the stored form of carbohydrates. In the absence of carbohydrates, the liver will produce ketones and burn primarily fats (triglycerides) for energy instead of carbohydrates. Generally, the fuel source will be based upon individual preferences and demands of the sport or activity. Shorter, more explosive activities such as hockey or CrossFit and long, endurance activities such as marathon running, use energy systems that rely heavily on carbohydrates for energy. The human adult can store 100-120 grams of glycogen. It is estimated the demands for very hard training athletes can reach in excess of 500 grams of carbohydrates per day (Ivy, 1991).
Overall consumption of calories seems to be the biggest mystery in nutrition for most people. There are numerous equations (ie: Harris-Benedict), calorie trackers, and apps that will generate a calorie total that is said to be ideal. These can be a good starting point, but an athlete needs to make frequent adjustments in calorie totals due to factors like sleep, energy levels, overall workout volume, stress, activities outside of exercise, etc. Generally a good starting point is to make sure you have your protein needs covered which will fall somewhere in between the recommended dietary intake (.8 g/kg/d) and the RDI for athletes (1.6-1.8 g/kg/day) depending on volume and intensity of activities. The remaining calories will be split between carbohydrates and fats. Traditionally, the leaner the athlete is, the more insulin sensitive they are and have a better ability of utilizing carbohydrates. Carbohydrate levels can also be increased on days with more exercise volume and decreased on days with less volume or rest days, which is called carb cycling.
Hopefully this will help clear up some of the confusion when it comes to nutrition. Generally, relying on whole foods (fruits, veggies, nuts, seeds, lean meats) is best, as they have the highest density of nutrients and should compose most of the athlete’s diet.
To put everything together, we will figure out the calorie needs for a moderately active female who weighs 150 pounds, is 5’8” and is 30 years old.
The first step is to figure out her Basal Metabolic Rate (energy use at rest) using the Harris-Benedict Equation:
BMR = 655.1 + (10 x 68.2 (wt in kg) + (6.25 x 172.7 (ht in cm)) – (5 x 30 (age in years) – 161
The next step is to calculate her calorie needs based on activity:
Moderate Exercise (3-5 days per week): BMR x 1.55 = 1198.8 x 1.55 = 1858 calories
1858 calories would be our athletes starting point for calories.
Next protein requirements:
1.6 g/kg/day = 1.6 x 68.2 = 109g of protein.
109g of protein x 4 = 436 calories. 1858 total calories – 436 calories from protein = 1422 calories left over for carbohydrates and fats.
Dietary References Intake Tables. (2005). Retrieved from: www.hc-sc.gc.ca/fn-an/nutrition/reference/table/index-eng.php
R.W. Morton, C. McGlory, and S.M. Phillips. Nutritional interventions to augment resistance training-induced skeletal muscle hypertrophy. Front. Physiol. 6:245, 2015.
J.L. Ivy. Muscle Glycogen Synthesis Before and After Exercise. (1991). Retrieved from: http://www.ncbi.nlm.nih.gov/pubmed/2011684