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Carbohydrates, one of the primary macronutrients, play a vital role in human survival. They serve as an energy substrate, and their quantity in our diet significantly impacts our overall health. This blog post will delve into the role of carbohydrates, particularly in relation to aerobic physical activity.
Carbohydrates are energy-rich macronutrients. They are produced by plant organisms and are essential for animal and human survival. Among carbohydrates, glucose is of paramount importance as it serves as the fuel for body tissues, including the nervous system.
Humans, unlike plants, cannot entirely meet their glucose needs through neoglucogenesis (the production of glucose from amino acids, lactic acid, and glycerol). Therefore, they must consume foods rich in carbohydrates, such as cooked cereals, legumes, tubers, fruits, and roots.
Glucose, derived from dietary carbohydrates and neoglucogenesis, is crucial for cellular respiration. In aerobic metabolism, carbohydrates, fatty acids, and some amino acids are processed into Acetyl-Coenzyme A and entered into the Krebs cycle. This cycle is responsible for recharging the transporters NAD and FAD, which are engaged in oxidative phosphorylation necessary for activating the ATP-synthetase pump.
The Krebs cycle operates as a perpetual ring, starting and ending with a molecule called Oxaloacetate. This molecule is essential for the proper functioning of the entire system. However, Oxaloacetate molecules often deteriorate and need to be replaced. The precursors from which Oxaloacetate can be obtained are Pyruvate (derived from glucose) and Asparagine or Aspartic acid (non-essential amino acids).
During prolonged aerobic physical activity, the presence or absence of Oxaloacetate can become a limiting factor. To ensure the mechanism runs smoothly, it is essential to guarantee the presence of its easiest and quickest precursor to use, i.e., Pyruvate obtained from glucose (carbohydrates).
Having highlighted why carbohydrates are necessary for prolonged aerobic physical activity, it's crucial to understand how many to consume, what type, and where to find them.
The quantity of carbohydrates in the diet is always empirical, making the application somewhat challenging. However, it is possible to state that carbohydrates useful for prolonged aerobic activity must be introduced before, during, and after the performance. The availability of glucose during performance depends on intrinsic muscle stores and glycemic homeostasis, both influenced by the diet and post-prandial insulin flows of the previous days.
The type of carbohydrate necessary for aerobic activity depends on the function they serve and the context. Under optimal conditions, carbohydrates to be taken before aerobic activity should have a medium-low glycemic index to distribute their perfusion in the body for the entire period of time preceding the performance. During the activity, carbohydrates should be of medium-high glycemic index for rapid absorption and use. After the activity, high glycemic index carbohydrates should be consumed immediately post-workout, and medium-low glycemic index ones should be introduced more than 60 minutes after the end of the session.
The most suitable sources of carbohydrates at various times are:
By keeping in mind these guidelines, it is possible not only to improve recovery and performance but also to compose a mildly low-calorie diet aimed at losing weight, in conjunction with aerobic physical activity, without risking muscle catabolism induced by carbohydrate insufficiency in the diet.