Everybody knows your metabolism slows down as you get older but the question is why? That may sound like an annoying question from a petulant toddler, but it’s actually a very important one to answer. Once you understand the underlying mechanisms behind why metabolism slows down with age, you can arm yourself with the right tools to slow down – or even reverse – an aging metabolism.
Understanding Human Metabolism
Despite what some people would like to believe, your metabolism is much more complex than a simple energy balance equation. Between thinking, learning, sleeping, moving around, and existing, your metabolism is the entire collection of physiological and hormonal processes responsible for everything that you do. In a nutshell, your metabolism is both responsible for and also the result of your very living existence.
That’s a big part of the reason why a younger person’s metabolism is so much more active – because they have a whole lot of living to do. From the moment you’re born until a few years after puberty, your body is constantly growing and changing and developing. But something strange happens once you reach your adult years – and your metabolism starts to slow down.
Your Activity Level Drops as You Get Older
Most children live a relatively carefree life, spending most of their waking hours running around and playing all day. As kids get older, they spend less time playing outside and more time developing their minds in school. Both activities – playtime and learning – burn a huge amount of energy in the human body.
But after children finish growing up, leave school, and enter the Adult World, they have to get a job and start making money. Most adults don’t have time to play outside all day the way they did as a kid. And let’s face it – most career jobs don’t put the same cognitive demands on our bodies that growing up and learning things in school did. The less you have to do, the fewer demands you make on your body and your metabolism. So your body naturally compensates by slowing things down.
Lifestyle changes aren’t the only thing that slow down your metabolism over time, though. Body composition has an impact too.
The Way Your Body Changes Over Time Also Slows Down Your Metabolism
As we discussed above, different tissues in your body place different demands on your metabolism. Some require more calories than others. And certain tissues alter your metabolism in ways that can slam on the metabolic brakes if you aren’t careful.
The Metabolic Demands of Muscle & Fat
There are two reasons that you burn more calories when you have more lean mass on your body: your mitochondria, and your hormones. Muscle cells contain a much larger number of mitochondria than fat cells. Mitochondria are organelles within each cell which produce energy so that the cell can live and thrive. Think of each mitochondria like a little car engine; the more engines you need to power, the more gasoline you need to feed them. That’s why muscle tissue burns more calories than fat – because fat cells contain substantially fewer mitochondria and don’t require as much energy.
Another difference between fat tissue and lean tissue is the effect each one has on your metabolic hormones. For example, muscle reduces levels of the fat storage hormone cortisol by increasing testosterone. Conversely, fat cells secrete chemical signals which boost ghrelin, your hunger hormone, and block the satiation hormone, leptin, from having an influence on the brain. This means that the more fat and less muscle you have, the fewer calories you burn and the more calories you’re tempted to consume. It’s a double whammy blow to your metabolism!
Are We All Doomed to Suffer a Slow Metabolism After a Certain Age?
The answer to that question is a complicated one. Yes, after a certain age, your metabolism will gradually slow down and there won’t be much you can do about it. But the age at which that happens is what is currently up for debate. With all due respect to the wannabe eggheads out there, anyone who says your metabolism will definitely start slowing down after age 35 by a specific percentage each year is full of baloney. Everyone’s body is different, and the diet and lifestyle choices you make have a massive impact on when and how drastically your metabolism will slow down. And we are definitely going to tackle that subject in some upcoming articles – so stay tuned!
