Making sense of metabolism

By: Alison Dunn Aug 30, 2010

Everyone talks about metabolism and weight loss, but what does it all actually mean?

Admit it. You've blamed weight issues on your metabolism. You can't lose weight because you have a slow metabolism. That skinny person you know eats whatever she wants because she has a fast metabolism. But do any of us really know what it means?

Metabolism is a scientific term for all of the catabolic (breaking down) and anabolic (building up) reactions that occur in the human body. Or, in simpler terms, it’s the series of chemical reactions in your body that convert food into energy.

Part of the confusion over what metabolism is comes from the distinction between your overall metabolism and your basal metabolic rate, or BMR. Also known as the resting metabolic rate, the BMR is how many calories the body burns at rest. Your BMR will tell you how many calories you need to eat to keep your heart pumping and your brain and body functioning.

BMR usually accounts for about half of your calories you burn during the day. So what about the other half? That’s part of your overall metabolism. It’s the energy you expend doing physical activity, which includes everything from walking up the stairs to working out at the gym.

It’s a pretty simple equation that runs your metabolism. The calories you take in from food must be equal to the calories you expend to maintain a stable weight. If there’s an imbalance in calories in and calories out, then you store those excess calories, primarily as fat.

What’s your metabolism?

How can you get a handle on your metabolism? First of all, metabolism is unique to every person. There are, however, a number of factors that will influence your metabolism, making you either more or less efficient at burning the calories you take in. Those factors include:

  • Age: Kids tend to have higher metabolic rates than adults, because of growth hormones. That’s usually why you find you can’t eat the way you could as a kid. What’s worse, as we age, our metabolism tends to slow down even more – approximately two percent per decade.
  • Gender: Wonder why your boyfriend can always seem to eat more than you without packing on the pounds? Well, it’s because metabolism is one area where women get the short end of the stick. Men tend to have higher metabolic rates thanks to testosterone.
  • Body composition: Having a higher percentage of muscle than body fat also determines a person’s metabolism. Muscle burns more calories even while at rest, so people with a higher muscle mass will have a higher metabolism.

Given that all those things will influence your metabolism, how can you find out your own metabolic rate? An easy way to find out is just by knowing how many calories it would take to maintain a stable body weight. Keep a food journal for two weeks detailing everything you eat and drink in that time period. Total up the amount of calories you eat every day, and, if you maintain a stable weight, that’s roughly how many calories your metabolism burns in a day.

Making the change

The good news is that you’re not stuck with your metabolism: it is possible to change your metabolic rate. While you can’t change factors like your age, your gender or your BMR, you can alter your lifestyle to boost your metabolism. It’s as simple as two key things: exercise and diet.

First and foremost, you need to do some resistance, strength or weight training. Lean muscle increases your metabolism and helps you burn more fat even while you’re sleeping. Also, don’t forget the cardio. By increasing your heart rate and getting your muscles spending energy, you will burn calories during the activity, as well as post-exercise.

Diet, too, is a critical factor in boosting your metabolism. Try eating small meals throughout the day to boost your metabolism. If you eat five to six meals at approximately 250 calories each, you’ll increase your metabolism. You’ll also stabilize your blood sugar and avoid binge eating. Choose a variety of foods for each meal, including whole grains, fruits, veggies and proteins, to keep your engine running smoothly all day.

But while exercise and diet are positive ways you can change your metabolism, don’t forget to avoid those things that can negatively affect your metabolic rate. Most importantly, never, ever, try to starve yourself in an effort to lose weight. Sure, it sounds like a logical idea: if, to lose weight, you have to burn more calories than you take in, you should lose weight even faster if you take in no calories. But that isn’t what happens. You end up putting your body in an energy deficit, and your body’s survival instinct kicks in and slows down your metabolism so you won’t burn up any of its precious fat stores.

A journalist with more than 10 years experience, Alison’s work has appeared in a number of top Canadian publications, including glow, Oxygen, Canadian Running and more. She is the former editor of a number of well-respected Canadian and American trade journals and recipient of a Kenneth R. Wilson Gold Award of Excellence in feature article writing. She is a part-time faculty member at Sheridan College’s journalism department, as well as an avid runner and fitness enthusiast.