Here we are, gazing at that little roll of fat around our middle, lamenting that we’ve aged out of a fast metabolism and this roll is here to stay. Wouldn’t that be the perfect answer if we could jump start our metabolism back to its original speed with lifestyle changes? Well, that’s not the right question. Folk lore and perhaps poor social media have led us to believe that our metabolism drops suddenly in our 30s and we’re doomed. In truth it hangs on tightly until age 60 or so.
So what is metabolism and how can we increase it? Scientifically, your body is a laboratory where chemical reactions take place every moment—breathing, moving muscles, building and maintaining bones, digesting food and transforming it into energy, and even thinking. All of this requires energy—which science calls calories—so we measure metabolism as the number of calories used to keep your body moving. Metabolism is broken down into three categories:
- Resting metabolic rate (RMR) (60 to 75% of your *total daily energy expenditure)
- Thermic effect of food (about 10% of your total daily energy expenditure)
- Thermic effect of physical activity (15 to 30% of the amount of energy you burn through movement of all kinds)
Lean body mass—aka muscle—genetics, age and body size are why your friend who is taller and muscular can eat an extra slice of cake without gaining weight and you can’t, assuming you are shorter and inactive. Our culture also assigns men as having faster metabolic rates than women and that’s simply untrue. For many, men happen to have larger bodies and more muscles than women. The bigger you are, the more cells your body has to fuel, and the more energy you’ll burn.
It seems hopeless, yes? But wait. That last paragraph was about lean body mass so if you begin strength training, you’ll increase muscle mass. Muscle burns 3x more calories than fat so lifting weights increases RMR by about 7%, or an average of about 100 calories a day. Not much but over time it adds up. And here is where you can have the most impact.
*total daily energy expenditure – what you need to eat in a day to fulfill all the needs of your body.