The following theoretical approach is a simplification, a popularization for educational purposes. It is with the aim of making the concepts simple, accessible, and applicable that I propose you approach practical sports nutrition.
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Nutrients
There are two main families of nutrients. Macronutrients, the only nutritional elements that provide energy, and micronutrients, which are "the others" and do not provide any energy. In nutrition, the amount of energy is measured in kilocalories (Kcal) (1 Kcal = 1000 calories = 4124 Joules). On the packaging of our food, we will learn to read that 100g of a given food provides a certain amount of Kcal.
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Macronutrients
Inseparable from all nutritional advice, carbohydrates, fats, and proteins are the superstar trio of nutrition. We look for them, we count them, we add them, we subtract them. One person will seek to add protein while another will hunt for fats. The issue? Calories and added value. Each macronutrient has a high nutritional value and a certain amount of calories.
1g of Carbohydrates = 4Kcal
1g of Fat = 9Kcal
1g of Protein = 4 Kcal
Carbohydrates: sugars or carbohydrates.
It is a combination of carbon, hydrogen, and oxygen atoms. There is a basic structure (CH2O) and variants where the number of carbon atoms gives each carbohydrate its specificity. We find monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Note that the term sugar only includes "what is sweet." The most well-known sugar is sucrose from the disaccharide family, which is white sugar. There are more hidden sugars, such as starch, which is the most common sugar in the plant kingdom and is found in abundance in all cereals (wheat, corn, potatoes, etc.). Lactose is also part of the carbohydrate family. Overall, in a "classic" European diet, nearly half of the energy is provided by carbohydrates, including 15% from sucrose. This high consumption of refined sugars is associated with a large number of modern human pathologies (cavities, diabetes, metabolic syndrome, etc.).
The apparent abundance of carbohydrate-rich foods and their obvious ease of preparation quickly made them the number one source of energy. Logically, when nutritionists became interested in the energy needs of athletes, the answer seemed obvious. "Athletes need energy to exert themselves: they should eat more carbohydrates." Unfortunately, this nutritional policy, which emphasizes the quantitative aspect of carbohydrates to the detriment of everything else, often masks the micronutrient deficiencies it induces. As long as the athlete "eats well," that is, eats more pasta than others, the question appears to be settled. As long as the athlete doesn't "gain fat," we assume they don't eat too much. During my consultations, athletes spontaneously talk to me about the quantity of pasta they eat. It's more appropriate to focus on what type of pasta and, especially, what they forget to eat.
As you can see, the importance given to carbohydrates in athletes' diets is too great. Not a race worthy of the name takes place without the "SSPP" (Sacro Sainte Pasta Party), and every parent is tempted to make their child eat pasta the day before their first soccer match. Carbohydrates are considered THE fuel for exercise, to the detriment of everything else. Physiologically, the body is capable of storing energy in the form of a certain quantity of glucose molecules called glycogen. This glycogen is stored in the liver and skeletal muscles. The main function of liver glycogen is to regulate blood sugar levels between meals, and muscle glycogen provides the energy essential for prolonged exercise in combination with fat reserves. This "energy reservoir," this glycogen reserve, is not unlimited. That is, we cannot force the body to store carbohydrates beyond what it can. There's no point in doubling your carbohydrate intake in the hope of having more energy for a marathon. Especially since the intestinal tract isn't necessarily able to handle large amounts of carbohydrates at unusual rates and times.
During exercise, the body metabolizes its energy from both its glycogen and fat reserves. It is now generally agreed that in terms of energy (and in other areas), quantity does not prevail over quality. We will see that incorporating a reasonable amount of carbohydrates and lipids with high nutritional density is the best strategy to adopt to provide the body with sufficient energy.
