It's a simple word that encompasses so much. Metabolism is defined as "the chemical and physical processes by which a living thing uses food for energy and growth." All of your body's natural processes—breathing, building new cells, repairing muscle, circulating blood, adjusting hormone levels—require energy. Thus, they burn calories. You may not think it takes a lot of calories just to stay alive, but the processes required to sustain human life are actually responsible for the majority of the calories we burn each day.
The number of calories your body burns while at rest in a neutrally temperate environment is known as your basal metabolic rate (or alternatively, your resting energy expenditure). Gender, genetics and body size all play an important role in your basal metabolic rate (BMR). According to the Mayo Clinic, basal metabolic rate accounts for roughly 70 percent of the calories an average person burns each day.
When people talk about "speeding up your metabolism," they're usually referring to increasing your BMR. There are very few people who don't find the idea of a higher BMR attractive, since it essentially means you'd be burning more calories at all times (including in your sleep). However, there are a ton of misconceptions about metabolism and the impact we can have on it.
Here are three metabolism myths that need to die immediately.
1. Thin People Have Lightning-Fast Metabolisms
"You see how thin so-and-so is? They've gotta have a fast metabolism."
You've surely heard something along those lines before. While many Americans believe that skinny people have faster metabolisms than big folks, the opposite is in fact true.
"Skinny individuals almost invariably have slower resting metabolisms; there is literally less of them to burn while at rest," Dr. Yoni Freedhoff, assistant professor at the University of Ottawa, told CNN. By skinny, we mean individuals who both have little fat mass and little muscle mass on their frame.
But what about two people with identical heights and weights but drastically different body compositions? The one with more muscle mass would be expected to have a higher BMR, but the difference is less than you may think.
In his paper "Controversies in Metabolism," Dr. Len Kravitz, Program Coordinator of Exercise Science and Researcher at the University of New Mexico, states that an extra 4.5 pounds of muscle mass would increase an average person's BMR by about 50 calories per day. That's equal to roughly seven almonds. So while it's an improvement, it's not exactly a dramatic one.
"It takes a fair amount of muscle to add enough calories to move (BMR)," says Dr. Mike T. Nelson, an exercise physiologist and member of the American College of Sports Medicine.
2. Skipping Breakfast is a Death Blow to Your Metabolism
Let's get this out of the way right now—there are plenty reasons to eat breakfast. "Breakfast is a way to get your fluid, fiber and protein quota for the day," says Leslie Bonci, RD and owner of Active Eating Advice. "Without it, you're shortchanging your body and your mind. You'll be tired and have more trouble focusing."
Research has shown that eating breakfast does indeed help you start the day sharper. A 2005 study found that elementary school kids who ate breakfast had better short-term memory than the students who didn't. A 1999 study found that eating breakfast helped people perform better on a spatial memory task than those who didn't. Breakfast eaters also reported a more positive and calm mood.
So breakfast is an important meal. You've probably heard that eating breakfast is critical if you want to jumpstart your metabolism for the day ahead, but that doesn't seem to be true. Skipping breakfast doesn't appear to have much of an effect on metabolism or weight loss. A 2014 study concluded that eating breakfast resulted in "no change in resting metabolism" amongst participants. A 2015 study found that "breakfast consumption was not consistently associated with differences in BMI or overweight/obesity prevalence" among Canadian adults.
A breakfast filled with whole foods that are rich in protein and fiber is an excellent way to start your day, no doubt. But skipping breakfast won't bring your metabolism to a screeching halt.
3. Eating 6 Small Meals a Day Will Kick Your Metabolism Into Overdrive
This one caught on big a few years ago, but new research has since debunked—or at least poked some serious holes in—the theory.
The idea is logical enough. By spreading an equivalent number of calories over six meals instead of three, our bodies are consistently being fed energy throughout the day. Therefore, they never have to go into "survival mode" and our metabolism can efficiently burn calories around the clock. In reality, the number of meals we eat doesn't seem to have much of an effect on metabolism.
According to Examine.com, an independent site that collates scientific research, "Eating food six times a day, or very high meal frequency, does not seem to increase the overall metabolic rate more than simply eating three times a day." Basically, it's the number of calories you eat each day that's important—not how many meals you spread them out over.
However, small meals aren't without their benefits. For one, they can help you avoid overeating. Second, smartly spaced small meals can better keep your blood sugar levels stable throughout the day, preventing rapid rises and falls in energy. That means less of that post-lunch afternoon grogginess.
Photo Credit: Voyagerix/iStock, Champja/iStock, Shironosov/iStock, Tataks/iStock
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