Why Different Athletes Need Different Diets
by Dr. Robert G. Silverman
If you were to gather a soccer player, a powerlifter, a rower, an 800-meter sprinter, and a tennis player in a room, there would be more differences among them than just their sports. Each athlete also needs to eat differently based on the energy system used during exercise. As a sports nutritionist, I work with competitive athletes of all types. Let’s take a closer look at energy systems and how they correlate to different types of athletes. Always consult your primary care provider before participating in any new exercise routine or physical activity.
Energy systems and their characteristics
There are three types of energy systems: phosphagen system, glycolysis, and oxidative system. Each is characterized by its rate of adenosine triphosphate (ATP) production (also known as power), total ability to produce ATP (also called capacity), and fuels used.1 The phosphagen system is characterized by a very high level of power, very low level of capacity, and using creatine phosphate and stored ATP as fuel. Glycolysis offers a high rate of power, low rate of capacity, and typically uses blood glucose and/or muscle and liver glycogen as fuel. An oxidative system is characterized by low power, very high capacity, and for fuel: adipose and intramuscular fat, blood glucose, and/or muscle and liver glycogen.1
Strength and weight division athletes
The phosphagen energy system is used during high-power exercises for a short duration of time. Powerlifters are often associated with the phosphagen system, but athletes who perform a golf swing or a short sprint also fall into this category. Typically, no carbs or fat are used in this phosphagen energy system. The regeneration of ATP comes solely from stored ATP, where it supplies energy for the first few seconds of effort.1
For strength athletes, I recommend a diet that provides adequate fuel to maintain a high level of lean body mass and allows for the proper amount and timing of protein and carbs to optimize a net protein synthesis response to training. In weight division sports, I place particular importance on diets that simultaneously achieve a proper weight while also having a positive impact on health and performance. Eating a pre-event meal as well as eating during an athletic event are critical for performance, as are following proper hydration strategies.
Characterized by all-out exercise lasting from 30 seconds to two minutes, glycolysis is the predominant system used for long-sprint athletes.2 These athletes—such as sprinters who run distances between 200 and 800 meters—use moderate power for a moderate duration and need carbs in the form of either blood glucose (sugar) or muscle glycogen.2
Endurance sport athletes
For sports that require high levels of endurance, the oxidative energy system is largely at play. In low power and long duration sports, such as soccer or marathon running, athletes—especially those who follow a ketogenic diet—use fat as the major fuel source, as well as blood glucose and glycogen.1 I recommend diets for endurance athletes that meet the following goals: 1) provide adequate fuel for endurance activity; 2) replenish glycogen stores; 3) help build and repair tissue; 4) maintain body weight; and 5) help maintain immune function. Food should be consumed before, during, and after exercise in order to maintain blood glucose levels, maximize athletic performance, and improve recovery time.
When it’s time to compete, endurance athletes should choose a preevent meal high in carbs, moderate in protein, and low in fat and fiber.3 During a race or game, endurance athletes should replenish carbs at a necessary rate.3 All postcompetition recovery meals should be rich in high-GI carbs and protein.3 It’s also critical for endurance athletes to mind their competition fluids. Athletes should work with a functional health practitioner to calculate their sweat rate and dehydration percentage in order to understand the amount of fluids needed for proper hydration and replenishment. Athletes should then consume the appropriate amount of fluids prior to competition, as well as afterward.
General rules of thumb
In addition to the specific needs of individual athletes and their respective energy systems, there are some general dietary rules that all athletes should adhere to. As a broad recommendation for carb intake, athletes should consume carbs three hours prior to exercise. During this time period, an adult athlete should eat one to two grams of carbs per kilogram of body weight. This represents that appropriate amount of carbs to raise glycogen stores at the onset of exercise. One hour or less before exercising, athletes should consume one gram of liquid carbs per kilogram of body weight. During competition, athletes should strive to ingest 30–60 grams of carbs per hour.4 This enables them to maintain blood glucose levels and optimize glucose uptake and oxidation.4 Maintaining glucose levels is key for all athletes during any increased exercise intensity.4 Immediately after training or competition, it’s recommended that athletes ingest at least 1 to 1 ½ grams of carbs per kilogram of body weight.4 As ever, timing is critical. Enhanced glucose uptake occurs within this time frame, and if carb delivery is delayed by two hours, the rate of glycogen recovery is slowed by as much as 50%.4
No two sports are the same—and based on the energy system used, athletes need different diets in order to optimize their performance. In some sports, such as tennis, there can even be a mix between two or more energy systems. Unfortunately, even athletes’ muscles don’t store much ATP; therefore, our bodies must synthesize, regenerate, and store it. Production of ATP is never achieved by the exclusive use of one energy system, but rather by the coordinated response of all three energy systems contributing to different degrees. Therefore, the importance of working with a Functional health practitioner and nutritionist persists—from the practice field to race day and beyond. You are what you eat, and performance athletes are certainly no exception.
- Brooks GA et al. Exercise Physiology: Human Bioenergetics and Its Applications.Mountain View, CA: Mayfield; 2000.
- Glaister M. Multiple sprint work: physiological responses, mechanisms of fatigue and the influence of aerobic fitness. 2005. Sports Medicine. 35(9):757–77.
- Kerksick C et al. Supplements for endurance athletes. Strength and Conditioning Journal. 2010;32(1):55-64.
- Wildman R et al. Carbohydrates, physical training, and sport performrance. Strength and Conditioning Journal. 2010;32(1):21-29.
Dr. Silverman is a paid consultant and guest writer for Metagenics.