science and physiology
Jeremy Watts, imm—May 9, 2020
Metabolism can be defined as the chemical processes that occurs in the human body to carry out functions necessary to live. An example is glucose or sugar, which is ingested and broken down into molecules and then undergoes glycolysis to provide energy for cellular function. When we get up and move, energy is required for muscles to do so. Metabolism creates this energy for our actions and every day living.
Many people understand metabolism in the context of the speed and ability of our body to break down and use the calories we eat, and then “get rid” of it through energy and digestion, or store it as fat. When we are young, our bodies and brains are growing and developing. We need a lot of calories filled with essential nutrients to help with this growth. Our physical growth naturally stops over time through hormonal regulation and, our metabolic requirements eventually and naturally changes with age. One of the reasons this happens is because after the age of 30 our muscle mass deteriorates by up to 5 pounds per decade without regular resistance exercises, and this statistic jumps up to approximately 10 pounds per decade for people over 60, according to research(1). This means that bone growth from muscular stress most likely isn’t occurring either because bones respond to muscular stress put on them. For example, if a person conducts resistance weight training, the bones have to become more dense to withstand the new stress introduced to the body so that they won’t break! Therefore the stronger the muscles, the stronger the bones! With age medical conditions like osteoporosis can develop, specifically in post-menopausal women, so developing good metabolic habits of eating and exercising may assist you ladies out there looking to reduce the likelihood of such ailments. The processes of breaking down/building up muscles and building bone density through exercise requires a significant increase in METABOLISM! Energy is required for the body’s response of positive stresses from various types of physical activity. So the more exercise and the greater the intensity, the more daily energy is required to repair and improve the body; ENERGY = CALORIES!!
Since our “Ultra-Consumer” American Appetites do not seem to diminish, our current health state collectively finds Americans in a positive energy balance (the bad positive) where we are consuming more calories than required for our overall metabolic needs. Considering that our diet consists of large amounts of sugars and carbohydrates, and 75 percent of Americans do not engage in recommended physical activity levels, we are storing these nutrients as fat because we are not utilizing them for energy during physical activity(2). Studies also show that muscles contribute to approximately 30 percent of the total calories that we burn at rest and our bone density in adults who do not perform resistance training may decrease by an alarming 10-20 percent every decade, and 20-30 percent per decade in older adults(3). So if we are not conducting resistance training and losing 5 lbs. to 10 lbs. of muscle mass per decade depending on age group, and we lose a significant amount of bone density during this time, what do we suppose happens to our metabolic rate? It decreases too.
Our bones and muscles are vascular, meaning blood flows through them to provide nutrients for cellular function. Remember that bone requires nutrients for growth—especially when doing prolonged resistance training. Fat tissue is different, however. It is avascular and stored in different areas of the body. Fat is potential energy and can be accessed by prolonged bouts of structured exercise, and extended fasting. In relationship to fat-burning and exercise, when we perform high intensity exercise such as resistance training, our body runs low on immediate energy like blood glucose (glycolysis) and must access fat cells to metabolize for energy. Oxygen is required for “fat-burning” (Beta-Oxidation) and so your heart rate increases to pump more oxygenated blood to the cells for this metabolic process to occur; you are now breathing harder! So we have targeted our fat-free mass and our various energy systems.
Muscle metabolism when inactive only contributes to approximately 6 calories of energy expenditure per pound of muscle during rest. However, active individuals see as much as 9 calories of energy expenditure per pound and if we are building muscle or increasing muscle mass, it equates to a whole bunch of extra calories.(3) This is also a significant increase in calories burned while resting and sleeping too; Resting Metabolic Rate (RMR). A resistance training regimen can increase your RMR by up to 200 extra calories per day which includes rebuilding muscle through protein synthesis, and bone through ossification. Other positive effects include reducing resting blood pressure and heart rate, while increasing good cholesterol (HDL). Another key outcome of this training is that it helps lower bad cholesterol (LDL) which is an indicator for the onset of a number of chronic illnesses and a marker for inflammation in the human body which is a great topic for another day!
Sincerely,
imm
1. Flack, KD, KP, Davy, MAW, Huber, et al. Aging, resistance training, and diabetes prevention. Journal of Aging Research 2011:127315, 2011.
2. Kahn, E., et al. Increasing physical activity: a report on recommendations of the task force on community preventive services. Centers for Disease Control and Prevention. Accessed January 22, 2020. https://www.cdc.gov/mmwr/preview/mmwrhtm/rr5018a1.htm.
3. Westcott, W. Keeping fit: it’s never too late to start strength training. Quincy College Fitness Center Information Newsletter. Accessed July, 2019.