NUTRITION - A GENERAL APPROACH
There is agreement when stating that diet influences performance. A well-planned nutritional strategy will help to develop any training program, whether it’s to be fit or to compete; will promote efficient recovery between sessions; It will reduce the risk of illness or overtraining, and help you achieve better performance.
Of course, each person has different nutritional needs, and there is no one diet that is suitable for everyone. Some athletes require more calories, protein, or vitamins than others, and each sport has its own nutritional demands. But, in general terms, it is possible to find broad scientific agreement regarding what constitutes a healthy diet for sport.
In order to achieve performance improvements and maintain good health, it is crucial that athletes cover their energy needs (calories) during intense training periods. Not consuming enough energy can lead to muscle loss, poorer performance, slow recovery, disruption of hormonal function, and an increased risk of fatigue, injury, and illness. Daily calorie needs will depend on genetics, age, weight, body composition, daily activity, and training program. From body weight and daily level of physical activity, it is possible to calculate the amount of calories we need per day.
Step 1: Calculate the basal metabolic index (BMI)
The BMI indicates the amount of calories we need while resting (to maintain heartbeat, lung breathing, body temperature, etc.). It makes up 60 to 75 percent of the calories burned each day. Men generally have a higher BMI than women.
Although there are more precise methods, as a general rule, the BMI uses 22 calories for every kilogram of women’s body weight, and 24 calories per kilogram of men’s body weight.
- Women: IMB = weight in kilograms x 22
- Men: IMB = weight in kilograms x 24
Step 2: Estimate the level of physical activity (LPA)
Physical activity includes all activities, from household chores to walking or training in the gym. The amount of calories we burn in any activity depends on the weight, the type of activity and the duration of that activity. A rough estimate of the activity involved in our lifestyle is as follows:
- Mostly inactive or sedentary (almost always sitting): 1.2
- Relatively active (includes walking and exercising 1 or 2 times a week): 1.3
- Moderately active (exercise 2 or 3 times a week): 1.4
- Active (intense exercise more than 3 times per week): 1.5
- Very active: (intense daily exercise): 1.7
Step 3: Multiply the BMI by the LPA to obtain the daily calorie requirements
Daily calorie needs are obtained by multiplying BMI x LPA. This figure gives us a rough idea of the amount of calories needed to maintain weight. If we eat fewer calories, we will lose weight; if we consume more, we will gain weight.
Carbohydrates are the most important fuel for physical activity. They are accumulated as glycogen in the liver and muscles, and must be replenished every day. About 100 grams of glycogen (the equivalent of 400 kilocalories), and up to 400 grams (the equivalent of 1600 kilocalories) can be stored in the liver in muscle cells. The role of liver glycogen is to keep blood sugar levels stable. When blood glucose drops, glycogen from the liver breaks down to release glucose into the bloodstream. The function of muscle glycogen is to make physical activity possible.
The more active we are and the more muscle mass we have, the more carbohydrates we will need. Experts today prefer to express carbohydrate requirements in terms of grams per kilogram of body weight.
GUIDELINES FOR DAILY INTAKE OF CARBON HYDRATES
Very light training (low intensity or low skill exercise)
|3-5 g / kg of body weight, per day
Moderate intensity training (approximately 1 h daily)
5-7 g / kg of body weight, per day
Moderate-high intensity training (1-3 h daily)
7-12 g / kg body weight, daily
Very high intensity training (> 4 h daily)
|10-12 g / kg of body weight, per day
Source: Burke, 2007.
To promote recovery after exercise, experts recommend consuming 1 to 1.5 grams of carbohydrates per kilogram of body weight per hour in the 30 minutes after physical activity, and then at intervals of 2 hours, up to 6 hours later. If you are going to re-train in less than 8 hours, it is important to start replenishing energy as soon as possible after physical exercise. During this period, moderate and high glycemic index (GI) carbohydrates (see p. 55) will allow for faster recovery.
It is recommended that, depending on the intensity and duration, the food prior to physical activity provides between 1-4 grams of carbohydrates per kilogram of body weight, and that they are ingested between 1 and 4 hours before exercising. For more than an hour activities, consuming between 30 and 60 grams of carbohydrates will help maintain blood glucose levels, save muscle glycogen, delay fatigue and increase endurance. The amount depends on the intensity and duration of the exercise, and it is not related to body size. It is recommended to combine several types of carbohydrates (for example, glucose, fructose and sucrose) to increase their absorption and oxidation rate while activity lasts.
Protein amino acids are the building blocks of new tissues and serve to repair the body’s cells. They are also used to make enzymes, hormones, and antibodies. Proteins are also a (small) source of energy for muscles. Athletes have higher protein requirements than sedentary people. Extra protein is needed to compensate for the increased muscle breakdown that occurs during and after intense physical exercise, as well as to build new muscle cells.
It is recommended to ingest between 1.2 to 1.7 grams daily of protein per kilogram of body weight, which is equivalent to 84-119 grams daily for a person of 70 kilograms. This is considerably more than what it is recommended for a sedentary person, who needs about 0.75 grams of protein per kilogram of body weight per day. It is better to distribute protein intake throughout the day than to consume it in just one or two meals. Experts recommend 20 to 25 grams of protein with each main meal, and also immediately after physical activity.
Several studies have shown that a combination of carbohydrates and protein, taken as soon as exercise is completed, improves recovery and promotes muscle growth. The types of protein ingested after physical exercise are important: those of high quality, especially those of rapid absorption (such as whey), are considered optimal for recovery.
Some athletes follow high protein diets because they believe that an extra amount will allow them to get more strength and muscle mass, but this is not true. What causes muscle growth is the stimulation of muscle tissue through exercise, not the extra protein. Because there is protein in many types of food, most people — including athletes — eat a little more protein than they need. This is not harmful because the excess is broken down into urea (which is excreted) and energy, which is either used immediately or stored as fat if the calorie consumption is greater than the energy expenditure.
Consuming a little fat is essential because it is part of the structure of all cell membranes, brain tissue, neuronal sheaths, and bone marrow, and because it serves to protect the organs. The fat in food provides essential fatty acids and fat-soluble vitamins A, D and E, and it is an important source of energy for sports activity. In general, it is recommended that fat provides between 20 to 35 percent of the total caloric intake of athletes, that the proportion of energy from saturated fatty acids is less than 11 percent, and that the majority comes from unsaturated acid fats. Omega-3 fatty acids can be especially beneficial for athletes, since they are attributed certain benefits such as increasing the arrival of oxygen to the muscles, improving performance, speeding recovery and reducing inflammation and joint stiffness.
We should make sure we are well hydrated before we start training or competing, and try to minimize dehydration during physical activity. Severe dehydration can result in decreased stamina and strength, as well as heat-related illnesses. It is recommended to limit dehydration to no more than 2 percent of body weight.
We must also prevent hyperhydration before and during exercise, especially in events lasting more than four hours. Drinking water consistently can thin the blood, thereby lowering sodium levels. Although this is rare, it is potentially fatal. Sports drinks that contain sodium are beneficial when sweat losses are high, for example, during intense activity of more than 60-120 minutes in duration, because their sodium content will promote water retention and help prevent hyponatremia.
After exercising, we need to replace water and sodium to restore our normal hydration. This can be accomplished through normal food and drink practices, if there is no urgent need for recovery. However, for a quick recovery, or if we suffer from severe dehydration, it is recommended to drink between 450 and 675 milliliters of liquid for every 500 grams of body weight lost during physical activity. Lost fluid and sodium can be replaced with rehydration drinks, or with water along with salty foods.
VITAMINS AND MINERALS
Although intense exercise increases the requirements of various vitamins and minerals, if we follow a balanced diet and consume an adequate amount of energy to maintain body weight, we do not need to take supplements. Although supplementation may be useful in athletes who follow a strict diet, or when dietary intake or alternatives are limited (for example, by having to travel), there is little data to support that vitamin and mineral supplements improve performance. However, athletes must take special care of their calcium, iron and vitamin D requirements. Similarly, there is not enough scientific evidence to recommend antioxidant supplementation to athletes. In fact, in the training phase, caution is usually recommended against antioxidant supplements, since oxidative stress can be beneficial for the adaptation of muscles to physical exercise.
THE PRE-COMPETITION DIET
What we eat and drink during the week before the competition can make a big difference in terms of performance, especially in endurance events and competitions lasting more than 90 minutes. The goal of the precompetitive diet is to maximize muscle glycogen stores and ensure adequate hydration. This can be achieved by reducing training, while maintaining or increasing carbohydrate consumption (7-10 grams daily per kilogram of body weight). Small, frequent meals are better than large meals. We must make sure we drink at least 2 liters of water a day, and on the day of the competition we must avoid unusual food and drinks.
HOW TO PLAN THE DIET FOR TRAINING
In general, it is recommended to follow the well-known food pyramid as a starting point for a diet suitable for sports performance. This pyramid classifies foods into 7 groups: fruits; vegetables; foods rich in carbohydrates; calcium rich foods; protein rich foods; healthy fats and junk food. The basic foods constitute the fundamental part of a healthy diet while those from the upper strata should be eaten sporadically and in small candidates.
Source: “La Guía Completa de la Nutrición del Deportista”. Anita Bean. Ed. Paidotribo. (Barcelona, 2005)