Human beings metabolize or burn calories in three basic ways and the combination of these three areas is what is known as our metabolism.
- Food processing (thermogenesis): this is the process of digesting, absorbing, transporting and storing the food you consume and converting it to energy.
- Physical activity: this can be broken down into two parts: exercise and non exercise. Exercise is intentional and deliberate activity designed to improve your physical fitness. These are activities such as strength training, running, swimming, biking, workout classes, etc. Non-exercise activities include a host of activities such as going up and down the stairs, moving from room to room, walking the dog, cooking dinner, playing with kids or grandkids, etc.
- Resting Metabolic Rate: this is the number of calories required to sustain life and execute metabolic functions such as breathing, cell regeneration, circulation, building and restoring lean tissues, immune response, etc. This is the largest portion of our metabolism and is responsible for the vast majority of our caloric expenditure.
Our resting metabolic rate is largely mediated by the amount of lean tissue (muscle) we have on our body. Put quite simply the more muscle we have the more calories we burn. Of course, this is at rest, thus if we burn more calories at rest we will in turn burn more with any activity we perform. A great analogy for this process is a campfire. Our resting metabolic rate is the fire itself and any muscle we add to our body is synonymous with adding logs to that fire. The more logs we add, the bigger and hotter the fire gets. This is precisely why if our goal is to improve our body composition, performing resistance exercise is of the utmost importance.
Resistance exercise improves our resting metabolic rate in two ways.
- Acute (immediate) effect: when we perform a bout of resistance exercise we have an acute increase in our resting metabolic rate of roughly 9% for the ensuing 72 hours.
- Chronic (additive) effect: this is the additive effect of adding more muscle tissue to our body (more logs to the proverbial fire) and effectively increasing our resting metabolic rate over time (bigger and hotter fire).