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"Just because you don't believe in something doesn't mean it isn't true." - Albert Einstein

Metabolism

Metabolism is the biochemical process of converting and using energy to keep the body functioning1. Understanding metabolism is important for designing a fitness program to achieve results scientifically. Additionally, I can adjust parameters that are more likely to impact my results. A fitness program includes nutrition, exercise, and recovery considerations, not just exercise.

Energy Use

Imagine the human body having 37.2 trillion tiny engines call cells. Metabolism is the process of converting food or stored energy to power these cells to grow and repair tissues1. The body uses up to 70% of total energy for keeping the body alive at rest, 15% for digesting food, and 15% for other activities such as exercise2,3. Furthermore, muscle cells use about 6.5 calories per hour per pound while fat cells use about 1.2 calories per hour per pound.

Muscle burns 5 times more calories than fat.

Energy Sources

The body can metabolize three food sources: carbohydrate, protein, and fat. Carbohydrate and protein provide 4 calories per gram while fat provides 9 calories per gram5. Vitamins and minerals don't provide energy, but to help the metabolic process.

Energy Storage

If excess energy is available to the body, it will store it for later use by design. That's how we survived when food was scarce thousands of years ago.

Excess carb is stored as glycogen in muscles first, then in the liver, and finally as fat. Each gram of carb bonds with 3 grams of water when stored, resulting in 4 grams of body weight gain. Muscles can store about 500 grams of glycogen while the liver can store 100 grams; therefore, the body can store about 600 grams of glycogen or about 2,400 calories4,6.

Excess fat is stored as triglyceride in fat cells. The body can store almost unlimited amount of fat in fat cells that behave like balloons. Fat cells will grow to store fat or shrink to release fat. When all fat cells are full, the body will make more; however, fat cells will never disappear. Each pound or about 450 grams of fat can store about 3,500 calories6.

Excess protein is processed similar to excess carb - stored as glycogen in muscles first, then in the liver, and finally as fat6.

A sound fitness program must first address energy balance, then improve rest metabolic rate (RMR) by building more muscles.

Reference

  1. CrashCourse. "Metabolism & Nutrition, Part 1: Crash Course A&P #36." YouTube, YouTube, 28 Sept. 2015, www.youtube.com/watch?v=fR3NxCR9z2U.
  2. Blundell, John E et al. “Role of resting metabolic rate and energy expenditure in hunger and appetite control: a new formulation” Disease models & mechanisms vol. 5,5 (2012): 608-13. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3424457/. Accessed 29 Nov. 2018.
  3. Rose, Brent. "The Science of Fat." Gizmodo, Gizmodo.com, 4 Sept. 2018, www.gizmodo.com/the-science-of-fat-1517247620. Accessed 29 Nov. 2018.
  4. Jensen, Jørgen et al. “The role of skeletal muscle glycogen breakdown for regulation of insulin sensitivity by exercise” Frontiers in physiology vol. 2 112. 30 Dec. 2011, doi:10.3389/fphys.2011.00112. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3248697/ . Accessed 29 Nov. 2018.
  5. USDA. "How many calories are in one gram of fat, carbohydrate, or protein?" National Agricultural Library. https://www.nal.usda.gov/fnic/how-many-calories-are-one-gram-fat-carbohydrate-or-protein. Accessed 29 Nov. 2018.
  6. Youdim, Adrienne. "Carbohydrates, Proteins, and Fats". Merck Manual. Dec. 2016. https://www.merckmanuals.com/home/disorders-of-nutrition/overview-of-nutrition/carbohydrates,-proteins,-and-fats. Accessed 29 Nov. 2018.
Disclaimer: I have no formal education in biochemistry, nutrition, or sports science. These are my personal notes from what I believed to be reliable sources. Please consult your doctor before adjusting your lifestyle.