Discover the truths and myths about your metabolism

Author: Canadian Living


Discover the truths and myths about your metabolism

This story was originally titled "Burn, Baby, Burn!" in the May 2011 issue. Subscribe to Canadian Living today and never miss an issue!

When it comes to laying the blame for weight woes, metabolism makes a nice, easy – and vague – target. We know it has something to do with burning calories, and that having a fast one is "better," but beyond that, it's a little murky. So, what is metabolism, really?

Think of your body as a furnace. You put in fuel – calories from food – and your body converts it to energy, producing heat as a result. Your basal metabolic rate (BMR) measures the fuel requirements of that furnace – the number of calories you burn each day to meet your body's basic energy needs for breathing, cell repair, growth, temperature control and blood circulation. These life-sustaining functions account for as much as 60 to 75 per cent of the calories we burn each day.

The common assumption that this furnace burns at a rate that's beyond our control – that we're either gifted (or cursed) from birth – makes metabolism the perfect scapegoat when we pack on a few extra pounds. But contrary to popular belief, we can exert some degree of control over how that furnace runs. Sure, there is a genetic component to our individual metabolic rates, but our lifestyle choices – physical activity and nutrition – play a huge role in maintaining a healthy metabolism. Separating fact from fiction is the first step in making your metabolism work for you.

What you've heard: "She's so skinny! She must have a fast metabolism."

The real deal:
Along with height, sex and age, weight is one of the factors involved in calculating an individual's BMR, but the relationship between weight and metabolism is the opposite of what you might expect, says Jason Hagen, a certified exercise physiologist and founder of FitMetabolism, a Calgary-based exercise physiology and lifestyle clinic. "A smaller person may naturally burn fewer calories per day, whereas an obese person burns more calories," he explains. Since the BMR measures the number of calories needed to maintain basic body processes, it makes sense – more calories are required to sustain people with larger frames.

Page 1 of 3 Do you blame your age as the root of your slow metabolism? Find out why that might not be true on page 2.

When it comes down to it, the secret behind that slim figure you're seeing may simply be that she moves more. "If you're active every day, your bones and muscles are stronger," says Dr. Mark Tremblay, director of the Healthy Active Living and Obesity Research Group at the Children's Hospital of Eastern Ontario Research Institute in Ottawa. "Any time the architecture of the body is more robust, you'll have an improved metabolism." So it's very possible that a brisk metabolism may be the result of – rather than the reason for – a lean physique.

What you've heard: "After I hit 30, my metabolism crashed. It's an inevitable part of getting older."

The real deal: Although you may not be able to burn off that slice of pizza as quickly as you did in your teens, it's not just the passage of time that's to blame. A person's BMR tends to drop by two to three per cent each decade after age 20, but according to Hagen, this is mostly due to a corresponding decrease in muscle mass. This also explains why men – who tend to have greater muscle mass – generally have a higher metabolic rate than women.

"Muscle burns more calories than fat, even when you're at rest," says Hagen. "To help counter the metabolic decline [that comes] with age, you actually need to gain weight in the form of muscle."

The best way to build this metabolism-boosting muscle is via proper nutrition and strength training (working against your own body weight to tax your muscles). Hagen suggests targeting large muscle groups such as the quadriceps, glutes and back muscles with squats and lunges. Even everyday activities like lugging groceries, lifting kids and gardening can help build strength.

Page 2 of 3 – Curious to know your BMR? Find a link to calculate your BMR on page 3.    

What you've heard: "My metabolism's been thrown off by a hormone imbalance. That's why I tend to keep weight on."

The real deal: Thyroid hormones do indeed play a huge role in controlling our BMR – a sluggish thyroid can slow down metabolism, while an overactive thyroid speeds it up – but these hormonal irregularities are just that: irregular. Despite being relatively rare, thyroid disease can often be detected with a simple blood test, and is worth checking out if it's a concern. "People know their own bodies," says Dr. Sarah Muir, a family physician in Halifax. "If they're feeling ‘not quite right,' checking thyroid function is a good thing to do."

But maintaining healthy levels of metabolism-regulating hormones isn't entirely out of our hands. "Hormones respond to exercise," says Tremblay. "Estrogen and testosterone, which are anabolic or tissue-building hormones, do decrease naturally as we age, but we can help counteract that because they can increase with exercise." Tremblay says starting an exercise program – even during menopause – will help mitigate a hormonal metabolic slump.

What you've heard:
"I compensate for my slow metabolism by slashing calories. Skipping the occasional breakfast and lunch should do the trick."

The real deal: This is a total miss, according to Jacklynn Humphrey, a dietitian and nutritionist with Dartmouth, Nova Scotia's Community Health Team. "Think of your metabolism as a wood stove or campfire," she says. "What happens when you don't feed the fire regularly? It burns out.

"When you don't eat enough, your body compensates by going into survival mode," says Humphrey. "The body lowers its metabolic rate, and you start using muscle as fuel instead of fat." After it grinds to a halt, it's hard to get your metabolism back in gear, which Humphrey says results in yo-yo dieting. "When you go back to eating regularly, you'll usually gain weight, because you've mucked up your metabolism. It's a vicious circle."

The key is to eat nutritionally balanced meals and smart snacks at regular intervals to keep the fires burning. In fact, the process of digesting the food you eat can account for as much as 10 per cent of the calories you burn each day – a significant built-in metabolic function.

Proper nutrition, paired with physical activity, is the best way to quit the blame game and take charge of your metabolism.

What's your BMR? For a close approximation of your basal metabolic rate based on height, weight, age and sex, check out

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Discover the truths and myths about your metabolism