Metabolic Aspects of Training

Learn the process your body undergoes during metabolic training.


By Jesse Nelson


Maybe you’ve heard talk about a “pregame meal, “preworkout” drink, what to drink/eat during exercise, or a “postworkout” protein shake. These meals/drinks are all nutritional ideas connected to the human body’s metabolism before, during, and after exercise.

The human body is endlessly striving, seeking, changing, craving, and reaching for homeostasis; a state of chemical equilibrium and balance. This drive for homeostasis is all-encompassing. The systems of our body are continuously working in a metabolic harmony. If one system starts to lag behind, or speed up ever so slightly, others feel it, and everything adjusts.

These processes of maintenance involves chemical processes that keep your body alive. Metabolism can slow down, speed up, or remain nearly constant. Like a car that uses gasoline as chemical energy to drive, we also use chemical energy.

The human body uses protein, fat, and carbohydrate for energy. We require these nutrients in order to preserve tissue, break tissue down (catabolism), and build tissue (anabolism). The words anabolic and catabolic categorize two of many thematic processes going on in the body, and are also known as metabolic processes.

Anabolic refers to constructive metabolism. Think of building muscle, or any other tissue in the body. Anabolic processes are happening in the body when it is building anything: muscle, bone, skin, liver tissue, kidneys, heart, lungs, and tissues. These processes are natural, healthy, and good. Without them we begin to lose the structure of organ systems in the body.

Catabolic means breaking down, or destructive metabolism. A catabolic process in the body requires the breaking down of a substance (like protein, fat, carbohydrate) in order to use it for energy. “Burning fat” is catabolic, and often desirable for a lot of people. In contrast, the breakdown of muscle is also catabolic. Muscle breakdown begins to happen during extended periods of fasting and overtraining.

Exercising well and having good nutrition is extremely beneficial in weight loss, which requires catabolic processes in the body.

Basically, exercise metabolism includes the study and use of three macronutrients (bigger nutrients), and three micronutrients (smaller nutrients). The big nutrients are proteins, fats, and carbohydrates. The smaller are vitamins, minerals, and flavonoids.

Applications and Suggestions

Protein metabolism - Proteins are molecules of many shapes and sizes that make up the structure of the body. Every cell in the human body contains protein. Eating foods that contain protein, helps to preserve the structure of the body.

Muscle tissue is preserved and built-up by protein molecules. As a rule of thumb, protein is broken down during exercise, and built up after. Weight training can cause microtears on the muscle tissue, depending on the intensity. Same thing can happen while running, sprinting, playing basketball, hiking, skiing, doing pushups, etc. These microtears need to be repaired, and guess what material is used for the repair? Protein molecules.

Generally speaking, the exact amount of protein to ingest depends on the intensity and intent of a person’s workout program. People who want to add muscle, tend to eat more. They also will need more around harder workouts, and less around lighter workouts. People more interested in weight loss, dieting, and light exercise might only need enough to maintain the muscle mass that they already have. One important thing to remember is excess protein will often be converted to fat for storage. Get advice from a healthcare professional or nutritionist, before making any dramatic changes.

Fat and its metabolism ( fat burn) is essential to the human body. It is used for the storage of energy, insulation, and padding around vital organs. It is also important for the creation of hormones, and the storage of vitamins and minerals. Even though fat is often considered evil, it is absolutely vital for sustaining life.

It is just as important for the body’s function and metabolism as protein and carbohydrates. They are all needed. A gram of fat holds 9 calories, in contrast with protein and carbohydrate, which each hold 4 calories per gram. Excess intake of carbohydrate and protein will often be converted to, and stored as fat. The difference is that fat does not need to be converted in order to be stored, requiring less energy. For this reason, it is easy to add fat mass to the body.

Carbohydrates are our “daily bread” and normally, the main source of fuel from day to day. Along with protein, it is recommended to consume carbohydrates directly before, and after bouts of exercise. Carbohydrate molecules break down into glucose, which is the exclusive energy source needed for the brain and eyes to run properly. Hypoglycemia, or low blood sugar, causes dizziness in a person because the brain is receiving reduced amounts of glucose (blood sugar). Insulin works directly with, and according to the amount of, carbohydrate entering the bloodstream.

Carbohydrates (“carbs”) are also generally feared, but are just as essential and necessary as protein and fat. Muscles run on carbs during exercise. Carbs are stored in the muscle and liver as glycogen, or “muscle sugar”. Stored glycogen is the first energy source to burn as the muscles begin to work.

Getting sugar into the bloodstream can be advantageous before exercise for more energy. After exercise, the store of glycogen needs to be replenished in preparation for the next activity.

Here are some examples of how the three macronutrients work together:

Muscle, which is made up of protein, runs first on carbohydrate (glycogen). As the duration of exercise continues, fat starts to breakdown throughout the body for the use of energy.

Excess amounts of both protein and carbohydrate can be converted to, and stored as fat. Excess dietary fat is stored as fat, and contains twice the amount of energy than protein, or carbohydrate. Fat also requires the least amount of energy to be stored as fat. The brain and eyes run on carbohydrate, in the form of glucose. During starvation, tissues made of protein start to breakdown, in order to fuel the brain. Fat storage also breaks down.

Challenge: write down your fitness, sport, or dietary goals. Take your goals to a registered dietician, nutritionist, or doctor and ask what percentage of your diet should be made of protein, of fat, and of carbohydrate. Ask them what foods are good sources of each. Take note and try out what is recommended.

See how you feel. Is there any change in your energy levels? Do you feel stronger or weaker?

Make note of the way your body feels. Read and research. Keep trying until you find what works for you, to meet your goals.

Jesse Obed Nelson has been a Certified Strength and Conditioning Specialist since 2009, soon after graduation in Physical Education at Utah State University. He went on to complete a master’s degree in Sports Conditioning and Performance from Southern Utah University, where he was able to publish his thesis, on the topic of agility development in high school soccer players. His favorite activity throughout his life has always been snow skiing, and he lives a 15 minute drive away from the base of Sundance Ski Resort, Utah.

Third Photo Credit: larik_malasha/; Fourth Photo Credit: Africa Studio/; Fifth Photo Credit: Komkrit Noenpoempisut/