Basics of (Sports) Nutrition

German Clénin 5. April 2017

To meet the demands of daily training and competition and to support recovery after the effort, you need to provide your body with enough energy through an adequate uptake. Dietary energy is like fuel to your body. It’s obvious that training and competition generally increase the daily energy requirements and, depending on the type, duration, and intensity of your sports discipline, you need to adapt your intake of food and beverages. The three main nutrients from our diet that supply the body with energy are carbohydrate, fat and protein. These three can be obtained by eating food as proposed by the Food Pyramid for Athletes.


Carbohydrate, in the form of glucose, is the main fuel used during exercise and is stored in muscle cells and the liver as glycogen. When physically active, you use the stored glygocen. The muscles and liver can usually store enough glycogen for about 60 to 90min (up to max 120min) of high intensity exercise. If you have ever ‘hit the wall’ while exercising, you know how body glycogen depletion feels. As carbohydrates help the metabolism of fat, and you’ve just run out of carbohy- drate as a fuel, nothing works. The fat metabolism cannot take over, until some carbohydrates are digested and are ready, in the form of glucose, to restart both metabolisms. The glycogen stores need to be continuously replenished between or during exercise sessions by eating and drinking foods high in carbo- hydrate. This supplying of carbohydrate will significantly delay the depletion of body glycogen, thereby delaying muscle and general fatigue and sustaining high level performance. Because the body requires less oxygen to burn carbohydrate (in comparison to fat and protein), carbohydrate is considered the body’s most efficient fuel source.

How to Indicate and Measure Energy

Energy is officially measured in joules. However, as it was measured in ‘calories’ for many, many years, the common expression is still calories.

1 calorie = 4.184 joule*

*This equation is correct. Our food and the common practice however says ‘calories’ or ‘joules’ but in fact we are talking about kilocalories (kcal) and kilojoule (kJ), which means nothing else than 1,000 of them.


Protein is the nutrient whose main function is to build up and repair muscle and body tissues after exercise as well as to synthetise important enzymes and hormones. Under normal circumstances, it hardly contributes as an energy fuel in sports. In some situations, however, especially when we eat too few calories daily, or during latter stages of endurance exercises, glycogen reserves are completely depleted, and skeletal muscle may be broken down and used as fuel. The latter is a possibly necessary sacrifice in competition, the first is undesir- able condition in daily training (compare chapter ‘Underweight – What to Do’ and ‘Female Athlete Triad’). A well-balanced diet covers the protein needs of most of athletes: chicken, turkey, beef, lamb, pork, fish, eggs, dairy foods, and plant sources of protein like tofu, nuts, and seeds. Protein is formed by various combinations of little chemical structures called amino acids. Some amino acids are produced in our body by rearranging the structure of other compounds, while other amino acids (called the essential amino acids) can only be obtained by eating food. Protein from animal foods presents a good variety of amino acids, including the essential ones, while protein from vegetable foods show a different pattern: they usually contain one (or more) of the essential acids in abundance but not the variety. This may be a problem if vegetables make up most of your diet, like for vegetarians. However by thoroughly mixing different plant products, it is possible to cover the needs for proteins, including the essential amino acids as different plants contain different proteins and many are complementary. The usual targeted recommended dietary intake (RDI) of protein for recreational sport activity is 1g/kg bodyweight. For team athletes, strength-training athletes in a maintenance phase and endurance athletes with a moderate maintenance program, the protein requirement is slightly higher (RDI 1.2–1.4g) and it will be covered by basic nutrition alone. During growth and adolescence (RDI 2g), but also in strenuous endurance or strength-training athletes (RDI 1.7g), protein need is further increased, which needs thorough planning to integrate the rec- ommended four portions of protein by alternating one serving of meat, fish, eggs, cheese, or plant source of protein. In these latter situations, a selective additional protein supplementation to meet the RDI may be considered.


Fat provides the main fuel source for the long term and is essential for the delivery and uptake of fat-soluble vitamins. Fat provides more than twice the potential energy that protein and carbohydrate do (9 calories per gram of fat versus 4 calories per gram carbohydrate or protein) and is a virtually unlimited source of energy for athletes, as there is enough fat stored in muscle fibres and fat cells to supply more than 100hours of sport activity. To fuel exercise, however, fat needs sufficient oxygen to be consumed simultaneously. So fat fuels low or moderate intensity activity and helps endurance by sparing glycogen reserves even in high-intensity exercise. Most of us have sufficient energy stores of body fat, and it is important to know that the body readily converts and stores excess calories from any source (fat, carbohydrate or protein) as body fat.
 You should include moderate amounts of healthy fats into your daily diet, such as nuts, plant based oil (e.g. canola or olive oil), one portion of butter or spread (10g). For each additional hour of exercise, a ½ serving should be added. This contradicts the myth that fats are ‘bad’. This perception is wrong and recent studies have underlined the importance of a reasonable fat uptake. What it still true, however, is that fat in biscuits, chips, and deep fried food, and abundant fat in animal foods (e.g. salami, sausages) can be enjoyed, but in reasonable amounts.

Frequently asked questions – myths and facts

  1. One of the most common questions in consultations is: Why was I on my last legs? Why did I have this weakness? Shouldn’t I take some supplements?
    A shared observation among many nutritionists and sports medicine physicians is that sportsmen and women quite frequently suffer a break in their energy supply chain and they strongly believe that this must be related to a specific deficiency, possibly treatable with a supplement. Even with extensive lab tests, we very rarely discover a particular deficiency in these situations. But looking at the food and beverage intake of the particular day, and the day before, we mostly observe quite relevant errors in the management of the energy supply in general.
    - Inadequate energy intake for the whole day in long competi- tions
    - Missed meals not adequately replaced
    - Bad planning (‘we just ate a bit, when we had time’ or ‘there wasn’t anything else available on site but hot dogs and French fries’)
    - Irregular hydration and irregular nutrition the days before competition due to travelling or stressful days
  2. Dietary fat and weight: Athletes wanting to reduce body weight and, in particular, body fat levels ask, ‘What should I do? I have reduced my fat intake and still my weight is not moving.’ First of all, we need to check the athlete’s goals before asking this particular question. This goes with checking if a weight reduction is really needed. Secondly, we need to address the misconception of fat being the only element re- sponsible. All three types of fuel: carbohydrates, proteins, and fats all contribute to energy uptake. If energy uptake is greater than energy expenditure, the remaining calories will independently from their origin, be stored as body fat. So it’s about a simultaneous moderate reduction in energy consump- tion and a moderate rise in energy uptake (see chapter ‘Being Overweight – What to Do’).
  3. Sports nutrition = carbohydrates. There’s a strong belief that, for sportsmen or women, concentrating exclusively on carbohydrates is the right thing to do. Very recently, a group of scientists proposed the opposite—to concentrate on mainly fat instead. As carbohydrates (or fat) would be the only source that energy metabolism is grounded in.

It’s true that carbohydrate has a central role in energy metabolism for exercise and recovery, and, on a quantity basis, is the most important nutrient in sport. But as outlined above, to believe in this equation would be a misconception and wilful neglect of the importance of fat and protein, as their essential function cannot be replaced. Nutrition in sports is an ‘as well as’ function, very much like: Sports nutrition = carbohydrate + fat + protein.

In conclusion, nutrition in sport is about having balance. For this purpose the Swiss Society of Nutrition, and in particular the Swiss Forum for Sport Nutrition, has created the Food Pyramid for Athletes’. This pyramid gives an excellent overview on a well-balanced diet with sport performance in permanent focus. And you don’t need to learn percentages by heart, you may if you like, but be conscious about your nutrition and follow these recommendations. It is in my opinion a good idea to work this pyramid through, read it, and apply it. When you have questions, discuss them with your sports medicine physician Sports Nutrition and a sports nutritionist. Adopt this pyramid as your specific nutritional target, a blueprint of how it needs to be, and you will be rewarded by having your energy intake organised. Food Pyramid for Athletes: Food Pyramid

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