Updated: Jun 4, 2021
Carbohydrates, fats, and proteins nutrients are all capable of providing our body with the energy we need not only for intense exercise but also for our body to function properly during rest. When consuming these nutrients, they are broken down inside the digestive system and transported to the muscles. The body uses mainly the energy inside carbohydrates and fats to produce ATP (for more about ATP read the blog: the science behind calories).
The use of protein for energy is much less than the other nutrients. The body only uses protein in extreme cases when energy stores derived from carbohydrates (glycogen) and fats are depleted, such as during very prolonged or intense exercise, during times of starvation, and when a person follows a low-carbohydrate and fat diet. People follow a low-calorie diet or a low-carbohydrate diet hoping that instead, they will use stored fat as energy. However, the weight that they lose will come predominantly from muscle since protein will be used as energy instead of maintaining and building new muscle tissue.
Another nutrient that contains energy is alcohol. Unlike the other nutrients, the energy from alcohol cannot be used by the muscles, even during intense workouts. Alcohol is transported to the liver, where specific enzymes can break down alcohol. Therefore, the calories that are found in alcohol take much longer to burn!
Thanks for reading, and as always stay fit!
Kerksick, C. M., & Kulovitz, M. (2013). Requirements of energy, carbohydrates, proteins and fats for athletes. In Nutrition and enhanced sports performance (pp. 355-366). Academic Press.