The role of diet & nutrition in sports performance

6 February 2020

It is no secret that in the modern world of elite sports, nutrition has become a vital variable that can influence the performance of an athlete. It is not by chance that we often read about athletes’ strict eating regimen. Whether it is the intensive keto diet LeBron James used to lose weight, or Michael Phelps’ infamous 10,000 daily calories to fuel his 2008 Olympics efforts, the ideal diet plan will vary depending on the sport, desired goals, and specific personal preferences of the athlete. 

But what is exactly the role of diet and nutrition for sports performance? While there are numerous general health benefits to a good diet, there are 3 main purposes a nutrition plan has to fulfil in relation to sports performance:

  1.  Provide energy for training & competition: This sounds quite obvious, but It is not only essential for athletes to meet their daily caloric demands, but also the manner by which those calories are consumed. Macronutrients, micronutrients, ratios, meal timing & frequency, hydration, and supplementation are all factors that should be taken into consideration when crafting an optimal diet plan.
  2. Facilitate recovery after training & competition: after an intense match or training session, glycogen (or energy storage) in the muscles are depleted and some proteins in the muscles are broken down and damaged. By eating soon after (or even during) training or competition, those glycogen stores are replenished, which prevents muscle (protein) breakdown and accelerates recovery.
  3. Achieve & maintain optimal body weight & composition: it is important for athletes to achieve optimal body weight and body fat levels to maximise their performance. Even more importantly, a diet plan must be developed in a way that the athlete can effortlessly adhere long-term.


Arguably the most important macronutrient in any athletes’ diet, carbohydrates act as the main energy source for any physical activity. Generally speaking, carbs should be 55% to 70% of the energy source for an athlete. This is due to the fact that carbohydrates are the main source of glucose. Glucose is converted by the body into glycogen and stored in the liver and muscle tissues. Stored glycogen is then used as energy to fuel athletes during physical activities.


Protein is a critical part of a training diet and plays a key role in post-exercise muscle recovery and repair. Generally, strength and endurance athletes should aim for 1.5 – 2 g of protein per kilogram of body weight per day, which is rather easy to achieve. This is because protein needs are often already met by following a high and varied carbohydrate diet, as many carb sources also contain a good amount of protein.


Carbohydrates and protein are arguably the most important macronutrients in the diet of an athlete. But what role do fats play? Contrary to old beliefs and misconceptions, fats actually play a crucial role in a diet. Hormonal production, Joint structure and cell membranes are all dependent on fats. Moreover, many vitamins are fat-soluble, which means they need fat to be fully absorbed in the body.

The optimal fat intake is generally around 10% of total daily calorie intake. The most important factor to consider is the type of fat that is consumed.

Monounsaturated and polyunsaturated fats are what is known to be healthy fats. Saturated fats also carry health benefits but should be consumed in moderation, while trans fats, especially artificial ones, should be avoided as they have been shown to increase harmful cholesterols, reduce the amount of beneficial cholesterol, while also increasing the risk of heart disease.


Pre Training / Competition

Athletes commonly load up on carbohydrates before a competition to maximise glycogen stores, particularly in endurance-heavy sports. According to articles by the Journal of Sports Medicine, benefits of pre-competition carb-loading include delayed onset of fatigue of up to 20% and improve performance of up to 3%.

Some studies also suggest that carbohydrates consumed before the sporting event should be low in the Glycemic Index. This allows a more sustained energy release during the physical activity, which can improve endurance and reduce fatigue.

During Training / Competition

It is not by chance that we often see athletes eat a small snack at halftime, consume an energy gel, or carbohydrate mouth rinse during a game. This is done to refuel their energy and replenish their glycogen store, while also preventing risks of hypoglycemia (low blood sugar).

Post Training / Competition

As previously discussed, it is important for athletes to eat after an intense training session or competition, to replenish glycogen stores, and promote recovery. Carbohydrate foods and fluids should be consumed ideally in the first one to two hours after exercise. A combination of carbohydrates of moderate to high Glycemic index and protein is generally recommended.


While there are general diet guidelines that can (and should) be implemented for optimising sports performance, it is important to understand that there is no one size fits all, and ultimately, nutrition and diet variables should be adjusted and tailored to the specific needs and preferences of the single athlete.