If you’ve ever thought about your weight in relation to your overall health (who hasn’t?), you’ve likely wondered how metabolism plays a part in the equation—or what metabolism even is.
Metabolism is the vital physiological process that drives our essential bodily functions, from “basic” actions (digestion, breathing, blood circulation, etc.) to complex pathways at the tissue and cellular levels and more energy-demanding actions, such as physical activity. “Metabolism isn’t just about weight. It actually has more to do with how our body uses the food we eat and converts it to fuel for energy,” shares Scheller.
Metabolism and metabolic rate are interlinking. A core factor of metabolic rate is basal metabolic rate (BMR); and it’s unique to you. Essentially, your BMR is the amount of energy your body needs to carry out essential functions (e.g., breathing, blood circulation, hormone regulation), even when it’s resting (and sleeping). In other words, the higher your BMR, the faster your metabolic rate (and metabolism).
One aspect that heavily influences BMR is your muscle content. Muscle is just one component of lean body mass, which is the weight of everything except body fat (i.e., muscle, body water, organs, skin, bones). The higher your muscle mass, the more energy, aka calories, your body burns at rest (this is known as your resting energy expenditure, or REE).
Because fat is not as metabolically active as lean muscle mass, the alternative is also true—if a body composition has a higher fat percentage, it requires less energy. As a result, individuals with a lower lean muscle mass have a lower BMR and a slower metabolism. And in the case of extra fat stores, that’s an example of too much energy storage.
As you can see, prioritizing strength (muscles), improving your metabolic rate, and increasing metabolism is the smart, sustainable approach (and it’s definitely not as simple as “calories in, calories out”).