Carbohydrate enemies of the diet? Should they be limited or not if you practice physical activity? The point with Dr. Jessica Ferrini, sports doctor
Why are carbohydrates important?
«Carbohydrates (also called carbohydrates) are part of the essential macronutrients, together with proteins, fats, fibers and water and, specifically, they are the ones most efficiently and easily used by our body to produce energy. In the absence of carbohydrates, our body uses the amino acids present in the muscle to provide substrates which, in turn, consume fat. For this reason, a diet that includes an adequate amount of carbohydrates saves protein, preventing the degradation of muscle tissue. Glucids also promote the release of insulin which, in turn, stimulates that of leptin, which promotes satiety and has a positive influence on thyroid function and hormone production. Also, foods rich in carbohydrates increase the speed of synthesis and release of serotonin and beta-endorphins, neurotransmitters that have an antidepressant and relaxing action, helping us sleep better (don’t be afraid to eat carbohydrates in the evening!).
Carbohydrate intake and sporting discipline
«Unlike what is said, a subject who trains at low intensity does not use only lipids and a subject who trains at high intensity does not use only carbohydrates, but the metabolism is a continuum and varies for each individual. In endurance sports, carbohydrates are essential (the guidelines recommend a quantity of 6-10 g per kilo of body weight per day) and in turn allow the use of lipid reserves for energy purposes. The intake of fast-absorbing carbohydrates (maltodextrin, sucrose) – often in liquid or gel form – during long-distance races is a common practice, although it requires complex intestinal training. On the other hand, in anaerobic alactic disciplines (powerlifting, weightlifting, diving: low repetitions, very high intensity) carbohydrates have a relatively little effect on performance, but – especially in subjects who train frequently – in any case it should not fall below 4.5-5 g per kilo of body weight per day. In anaerobic lactacid and mixed aerobic sports (calisthenics, body building and, in general, most sports): having well-stocked glycogen reserves (the muscle fuel tank) allows you to maintain an efficient level of performance, but the individual training session does not significantly affect them, therefore it is sufficient to introduce carbohydrates according to your food plan ».
Simple and complex carbohydrates: what changes in terms of training?
«All carbohydrates are sugars and are classified into simple (monosaccharides, disaccharides and oligosaccharides) and complex (polysaccharides). The body can only absorb monosaccharides (glucose, fructose, lactose, galactose, maltose) and must therefore separate the other simple forms and the complex ones (starch, fiber, glycogen), which are packets of monosaccharides joined together. What determines the nutritional value of carbohydrates is not so much the impact on blood sugar, but the additional micronutrients they contain (fibers, vitamins, mineral salts, fats). Simple glucids generate a rapid release of energy with an increase in glycemic and therefore insulin levels, while complex ones, on the contrary, staying longer in the intestine, promote a slower rise in glucose and insulin, allowing for a release of energy spread over time. When we do sports, adrenaline suppresses insulin, therefore the distinction between the two is lost and, indeed, the concomitant intake of complex carbohydrates could be counterproductive and cause gastrointestinal problems (therefore a decrease or interruption of performance) ».
Percentage and amount of carbohydrates in the diet
«Although carbohydrates should represent about 50-60% of the daily caloric intake, better if consumed for at least half in the five hours around training, this percentage can vary depending on subjective perception and genetic profile. For an active but sedentary subject (who does not practice sports), weighing about 70 kg, the recommended average quantity is 180-240 g per day. Obviously, in subjects who train, this quantity must be adjusted according to the intensity of the discipline. Therefore, the recommended daily range varies from a minimum of 3-3.5 g/kg of body weight to about 7-8 g/kg of body weight, up to 9-10 g/kg of body weight in endurance athletes. Generally, a predominantly carbohydrate metabolism is better tolerated in males, while in females the use of fats is more efficient and high loads of carbohydrates are less tolerated”.
Ideal sources of carbohydrates
«For the choice of carbohydrate sources, it is important to consider some characteristics of the various foods. The first is the amount of fiber necessary for the well-being of the intestinal microbiota, taking into account individual sensitivity and tolerance. The second is represented by the glycemic index (the speed with which a food raises blood sugar) and glycemic load (the quantity of carbohydrates that a food contains), which play an essential role in the diet of diabetic subjects or those with a reduced tolerance to glucose. The third is the type of saccharides (glucose, fructose, lactose, starch, etc.) present in foods, each with its own metabolism and a specific effect on our body (for example, fructose is metabolized in the liver, glucose from muscle tissue). In conclusion, the best sources of carbohydrates to take are whole grains (preferably oats and rice), vegetables and greens, fruit (in moderation) and legumes».
What is the ketogenic diet
«The ketogenic diet is an unbalanced diet in which carbohydrates are drastically reduced and which induces the body to form ketone bodies as an alternative energy source, starting from fatty acids or ketogenic amino acids. Physiological ketosis (different from diabetic ketoacidosis!) is an emergency metabolic mechanism and can accelerate weight loss, but should be followed in specific cases and for a limited period. In fact, it causes a state of acidosis in the body, which is unhealthy if continued over time, and symptoms that are difficult to bear for a long time (sensation of dry mouth, increased diuresis, acetonic breath and sweat, decreased appetite, decreased energy ). In addition to this, it promotes a reduction in the production of thyroid hormones and, although it can improve insulin sensitivity, it seems to worsen the affinity, and therefore tolerance, to glucose, a central factor for protein synthesis”.