Macronutrients

TL; DR:

1)    Macronutrients used by the body are carbohydrates, protein, and fat.

a.    Alcohol, while technically a macronutrient, would not be recommended to use as a primary energy source.

2)    Macronutrients serve as primary energy sources for activity in addition to other physiological functions in many body systems.

3)    As energy providers, macronutrient use coincides with energy system demand.

Macronutrients provide the body with Calories and serve as essential molecules in many physiological roles. Our primary macronutrients are carbohydrates, protein, and fat (to a lesser extent, alcohol). Each macronutrient has the potential to contribute energy for exercise or other body functions depending on the overall urgency for that energy. Higher intensity situations require faster, less efficient breakdown of macronutrients whereas more casual activity can rely primarily on slower, higher-capacity breakdown of macronutrients. As discussed in previous blogs, these scenarios (such as weightlifting or steady-state cardio) breakdown carbohydrates and fat depending on exercise intensity on a continuum of high-to-low intensity exercise. In this respect, macronutrient breakdown is highly related to the energy systems at play. Further, macronutrients therefore have unique and synergistic contributions to bodily functions – and their consumption in the diet should be scaled given the individual’s daily activities. Selective avoidance (or reduction) may have some benefits for some people, but overall, they are all important for most people, most of the time. The key is to understand that there is individuality of each person’s daily requirements.

Once phosphocreatine via the phosphagen system has been exhausted, and exercise appears to be continuing beyond the point where that system alone can sustain energy production, the breakdown of carbohydrates will begin to bridge the remaining energy gap to the completion of exercise, or the seemingly endless supply of energy can be produced by a combination of carbohydrates and fats via the oxidative system in lower intensity scenarios.

Carbohydrates in the form of glucose act as an intermediary, rapidly producing energy via the glycolytic system for high-intensity energy expenditure lasting approximately 30 seconds to two minutes, or, until such a time that the oxidative system can fully operate and sustain lower-intensity exercise.

Fat acts as a major contributing energy source for the oxidative system. Fats are much longer carbon-based molecules, and as such, account for a much higher capacity (total amount) of energy production than carbohydrates in lower intensity scenarios. While at rest, fat metabolism contributes the highest amount of energy for our activities.

While protein can be used as an emergency source or energy – this process is generally undesirable and requires greater energy input to yield a net output. This is because the body is designed to breakdown carbohydrates and fat as energy sources, thus, protein (or amino acids) must be physically altered into acceptable forms (carbohydrate or fat derivatives) before they can be used as an energy source. This is a highly inefficient process that is only drawn upon in emergency scenarios – the prolonged effect would be muscle wasting as the amino acids typically required for building lean tissue are being otherwise sequestered for energy production.

Determining an estimated macronutrient distribution and total Calorie count for your specific diet comes down to your individual energy expenditure per day and physical goals. These will be discussed as length.

Best,

Eric