Proper Fueling: Dietary Guidance for Athletes

By Published On: September 12, 2022

Diet and nutrition are vital to athletic performance. As well as providing the energy that athletes need to fuel their training and exercise, the right diet supplies the necessary building blocks for muscle growth and repair, supporting both performance and recovery.

While there are plenty of supplements on the market that claim to enhance athletic performance, the most important starting point for any athlete or coach is mastering the basics of a good diet.

Understanding the main food groups and their role in supporting our bodies is vital to helping athletes and their teams make the right choices. Carbohydrates, protein, fats, vitamins, minerals, and a sufficient intake of fluids provide the basis for any healthy diet.

Once those fundamentals are in place, a trained nutritionist or dietitian can help with fine-tuning a dietary plan to suit the individual needs of each athlete.

In this guide, we’ll look at the basics of diet for athletes, discuss how good nutrition supports performance, and give some tips on the timing and composition of meals.


Carbohydrates provide our bodies with their primary source of energy, especially during intensive exercise. As a result, getting enough carbohydrates in an athlete’s diet is essential to keeping them adequately fueled.

One gram of carbohydrate provides approximately four kilocalories of energy. This energy is stored as glycogen in the muscles and liver. It can be released more quickly than other forms of energy and is readily available for working muscles to use during exercise.

Research shows that keeping adequate levels of glycogen stored in the muscles helps to delay fatigue and gives a small boost to performance, especially for athletes competing in endurance events of 90 minutes or more.

The exact amount of carbohydrate an athlete should consume depends on multiple factors, including their training schedule, body composition, and fitness levels.

Current recommendations suggest an intake of 3-12 grams of carbohydrate per kilogram of bodyweight. As the intensity and duration of training increase, so too should the athlete’s carbohydrate intake. In general, carbohydrates should make up 45-65% of an athlete’s diet.

Good sources of carbohydrates include fruit, whole grains, starchy vegetables, and yogurt.


Many athletes know that protein is important for building and maintaining muscles, so it is no surprise that getting a lot of protein-rich foods is often a priority for them.

Protein is indeed a key building block for muscle growth and repair. It can also act as a secondary fuel source, although only once the body has run out of carbohydrate stores.

However, eating more protein than your body needs won’t help with muscle growth. Athletes do need a little more protein than non-athletes to support muscle repair, but most already get more than they need.

Excess protein is usually stored by the body as fat, so regularly consuming more protein than your body needs may lead to weight gain, as well as other health issues. As a rule, most adults should aim to eat no more than 2 grams of protein per kilogram of body weight each day.

Again, the exact amount of protein suitable for each athlete will depend on their individual needs. For example, the USADA suggests 1.2-1.4 grams per kilogram of body weight for endurance training, and 1.6-2.0 grams per kilogram of body weight for strength training (when the goal is to build muscle).

While protein supplements remain popular among athletes, the best sources of protein are whole foods, which also contain other nutrients that our bodies need. Lean meats, fish, legumes, whole grains, nuts, eggs, and dairy are all good options.

Protein should make up 10-30% of an athlete’s daily calorie intake, depending on their training schedule and goals.


While carbohydrates provide our bodies with their primary source of energy during intense activity, fat is also an essential fuel, especially during light to moderate exercise.

As athletes increase their fitness levels and are able to perform well at lower intensities, fat becomes more important as an energy source. Stored fat also provides essential energy for athletes competing in endurance and ultra-endurance events.

Fat plays other roles in our bodies too and is necessary for the absorption of the fat-soluble vitamins A, D, E, and K.

High-fat diets have become a topic of interest in recent years, for athletes and non-athletes alike. These diets are typically associated with lower carbohydrate intake. The combination can increase our bodies’ ability to use stored fat as an energy source.

Although evidence suggests our bodies can adapt relatively quickly to a high fat, low carbohydrate diet, this comes at the cost of our ability to efficiently use muscle glycogen as a quick fuel source for high-intensity activity.

While there are some scenarios where athletes may consider this an acceptable sacrifice, the current sports nutrition guidelines do not support these diets as a strategy for enhancing performance. Instead, the advice is that athletes should aim to get approximately 20-35% of their daily calorie intake from fats.

Of course, there are different types of fat and not all are made equally. While monounsaturated and polyunsaturated fats have many benefits for our health, saturated and trans fats raise LDL cholesterol levels and increase inflammation, which may slow recovery time.

Athletes should aim to reduce saturated and trans fats while maintaining a good intake of monounsaturated and polyunsaturated fats.

Sources of healthy fats include nuts and seeds, oily fish, avocadoes, and oils like olive, walnut, peanut, and sesame.

Vitamins & Minerals

In addition to the macronutrients discussed above, athletes need to ensure adequate levels of micronutrients like vitamins and minerals. These play an essential role in the healthy functioning of many of the body’s systems, including building and repairing muscles.

The most important vitamins and minerals for athletes include calcium, vitamin D, B vitamins, iron, zinc, magnesium, selenium, vitamin C, and vitamin E.

A varied diet that is rich in whole foods should provide adequate levels of most of these micronutrients. Fruits and vegetables are especially rich in vitamins and minerals, as well as dietary fiber, which is essential for gut health.

Eating a wide range of different vegetables and fruits also gives athletes access to the other phytonutrients present in these plant-based foods. These colorful compounds act as antioxidants, protecting our bodies against inflammation. As such, they may help to support recovery and reduce muscle soreness after exercise.

One potential exception to the food-first approach to nutrition for athletes is vitamin D. While some foods do act as a source of vitamin D, 90% of Americans don’t get enough.

Since vitamin D is vital to bone health, not getting enough may increase the risk of injury. Athletes may choose to supplement with vitamin D to ensure adequate levels. The Dietary Guidelines for Americans suggest aiming for 600 IU/day.


Keeping well-hydrated should be one of the greatest nutritional priorities for any athlete. Water is quickly lost during exercise and needs to be replenished to prevent dehydration.

Not only does dehydration impair athletic performance, through decreased oxygen and blood supply to working muscles, but it also can have serious implications for our health. Athletes need to keep up their fluid intake whether they are exercising or not and should pay special attention to how much they drink before, during, and after training and competitions.

Being thirsty is, sadly, not an accurate guide for when we need to drink fluids. Instead, athletes should pay attention to the color of their urine – dark urine is a sign of dehydration, while pale, clear urine indicates adequate fluid levels.

Athletes may also want to weigh themselves before and after exercise to track how much water they’ve lost. This water needs to be replenished within 6 hours at a rate of 16 to 24 ounces (480 – 720 ml) for every pound (450 grams) lost.

Water is the best choice if athletes are just trying to hydrate. However, during longer workouts or endurance events, athletes also need to consider replenishing electrolytes and carbohydrates. In these cases, sports drinks that contain 6-8% carbohydrates can help to maintain blood sugar levels.

As well as replacing fluids lost through exercise, athletes need to consume adequate fluids to meet their bodies’ basic needs. Aim for a daily intake of at least an ounce per pound of body weight (or 50 ml per kilogram of body weight), plus enough to replenish anything lost during physical activity.

What to Eat When

Of course, it isn’t just what athletes eat but when they eat it that affects their performance. There’s a balance to be struck between having energy available when they need it, but not causing stomach upset during exercise.

Ideally, athletes should aim to eat a meal 3-4 hours before a training session or event to ensure adequate glycogen stores to fuel their activity. Eating before exercise also helps to prevent hunger and low blood sugar.

This meal should focus on carbohydrates and a small amount of protein. Avoid heavy, greasy, or fatty foods which take longer to digest. The closer to an event the meal takes place, the smaller it should be to avoid stomach cramps or upset.

On event days, it is also best to concentrate on familiar foods that the athlete already knows they will tolerate well. The last thing you want is to try a new food and find it causes a bad reaction.

Many people exercise first thing in the morning, before eating breakfast. In this case, they’ll need to make sure the last meal of the previous day included enough carbohydrates to fuel their workout. Eating a small amount of carbohydrate a few minutes before training can also help to ensure adequate blood sugar and muscle glycogen levels.

After exercising, the priority is to replenish glycogen stores and support muscle repair. Athletes should aim to eat as soon as possible after exercise and should choose foods that combine carbohydrates and protein, aiming for a ratio of 4:1 carbohydrate to protein.

If eating straight away isn’t an option, a protein drink can fill the gap until the athlete can get to their next meal.

Some athletes prefer to eat smaller meals or snacks in the first few hours after exercise. Others may be ready for a larger meal. As long as they’re consuming high-carbohydrate foods during the 6 hours after exercise, athletes should follow their personal preferences and do what feels best for their own bodies.

During longer events, athletes will need to refuel to keep their energy levels up. However, solid foods can often cause stomach issues during exercise, so this is a time when most athletes will want to turn to sports drinks and gels instead. These are easily digested and provide a ready source of carbohydrates to fuel the remainder of their workout.

Of course, athletes should also aim to hydrate before, during, and after exercise to prevent dehydration and replace lost fluids.


As we’ve seen throughout this guide, whole foods are the best source of nutrients for athletes and should be the first port of call for meeting their dietary needs.

While there’s a thriving supplement market aimed at athletes, these are rarely required and can even cause harm.

Unfortunately, the supplement industry is only loosely regulated, and many products make misleading claims. There’s also a risk that supplements will be adulterated with banned or illegal substances.

Often, the claims made by supplement companies aren’t backed up by hard science. Marketing hype can create trends in supplement use without any evidence that these products are actually effective.

If athletes do choose to supplement, they should look out for products that have been third-party tested under schemes like Informed Choice and Informed Sport.

Of course, it is also wise to check the NCAA’s banned substance list before taking any new supplement. And do your research – don’t rely on claims made by the manufacturers but seek out independent studies to assess whether the supplement is likely to bring the benefits it claims.

Ensure Adequate Calorie Intake

Underfueling is a common issue for athletes, especially those who are concerned with their weight. Not getting enough calories can lead to fatigue, slower recovery times, difficulty gaining muscle, and increased risk of injury.

As well as eating a good balance of carbohydrates, fat, protein, and vitamins and minerals, athletes need to make sure they are getting enough calories overall to fuel their activity levels.

Many competitive athletes struggle to maintain their weight during the season and will need to account for this weight loss during the off-season. Any meal plan should consider an individual’s activity levels to ensure adequate calorie intake across the week.

Even if weight loss is the goal, a modest calorie deficit should be sufficient, especially when coupled with physical activity. Starvation diets aren’t sustainable and can impair metabolism. Aim for a deficit of around 400-500 calories a day and remember to adjust this if training intensity or duration increases.

Individual Plans

Although these guidelines provide a useful starting point for athlete nutrition, each person is an individual and their exact needs will vary depending on a wide range of factors.

For those interested in learning how to build nutrition programs tailored to an athlete’s individual needs, Concordia University Chicago’s MS in Applied Exercise Science offers a Sports Nutrition concentration.

This program is designed for anyone who aspires to provide sound sports nutrition information to athletes and physically active individuals. It will help you build your foundation of knowledge with principles based on the latest research and scientific evidence.

Fully online, the program is designed around the needs of working adults, so you can achieve your master’s degree while keeping up with other responsibilities.

Find out more here.

Purcell, L. K., & Canadian Paediatric Society, Paediatric Sports and Exercise Medicine Section (2013). Sport nutrition for young athletes. Paediatrics & child health, 18(4), 200–205.
Beck, K. L., Thomson, J. S., Swift, R. J., & von Hurst, P. R. (2015). Role of nutrition in performance enhancement and postexercise recovery. Open access journal of sports medicine, 6, 259–267.
Hawley, J. A., Schabort, E. J., Noakes, T. D., & Dennis, S. C. (1997). Carbohydrate-loading and exercise performance. An update. Sports medicine (Auckland, N.Z.), 24(2), 73–81.
Burke, L. M., Hawley, J. A., Wong, S. H., & Jeukendrup, A. E. (2011). Carbohydrates for training and competition. Journal of sports sciences, 29 Suppl 1, S17–S27.
Wu G. (2016). Dietary protein intake and human health. Food & function, 7(3), 1251–1265.
Burke, L. M., Whitfield, J., Heikura, I. A., Ross, M., Tee, N., Forbes, S. F., Hall, R., McKay, A., Wallett, A. M., & Sharma, A. P. (2021). Adaptation to a low carbohydrate high fat diet is rapid but impairs endurance exercise metabolism and performance despite enhanced glycogen availability. The Journal of physiology, 599(3), 771–790.
Burke L. M. (2021). Ketogenic low-CHO, high-fat diet: the future of elite endurance sport?. The Journal of physiology, 599(3), 819–843.
Sorrenti, V., Fortinguerra, S., Caudullo, G., & Buriani, A. (2020). Deciphering the Role of Polyphenols in Sports Performance: From Nutritional Genomics to the Gut Microbiota toward Phytonutritional Epigenomics. Nutrients, 12(5), 1265.

Request Program Information

View Concordia University Chicago Programs

Bachelor’s Programs


Graduate Certificates


Related Articles

Go to Top