Confused about how your metabolism works? We've got answers for you.

The word “metabolism” is often paired with terms like “diet,” “exercise,” and “weight loss.” But rarely is the buzzword thoroughly explained. As a result, there’s a lot of metabolism misinformation floating around out there.

The medical definition of metabolism? “The bodily processes needed to maintain life,” according to the Mayo Clinic. “Through the process of metabolism, your body turns the food you eat into the energy it needs. It’s a vital process for all living things, not just humans.” The term encompasses all continual chemical processes that keep you alive, including breathing, digesting food, and repairing cells.

In other words, without your metabolism you wouldn’t feel the energy boost you get from eating a meal. Health spoke to registered dietitian nutritionist Nancy Farrell Allen, a spokesperson for the Academy of Nutrition and Dietetics, to set the record straight on some of the most popular claims about metabolism thrown around these days.

MYTH: Skinnier people have faster metabolisms

It’s more about body composition than body size when it comes to metabolism, Allen says. “[Metabolism] depends on the composition of protein mass you have—muscle is more metabolically active,” she says, meaning the more muscle you have, the more calories you burn when you’re resting. It’s not true that the thinner you are, the faster your metabolism. It instead comes down to how muscular you are.

This is why lifting weights is one of the best ways to speed up your metabolism. “You’re going to have more muscle on you,” Allen says, and muscle burns more calories. Focusing solely on cardio won’t have the same effect.

MYTH: Your metabolism is genetic and can't be changed

Your genes do influence your metabolism—but they don’t affect it as much as the lifestyle habits you practice, according to Allen. The amount of exercise you get and the choices you make when you feed yourself are more important factors, and you (fortunately) are in of control them.

However, some genetic conditions can affect your metabolism. For example, Hashimoto’s disease, an often-hereditary condition that can result in an underactive thyroid gland, can slow your metabolism and lead to weight gain, according to the Cleveland Clinic.

RELATED: Is Your Metabolism Working Against You? 6 Simple Ways to Boost It

FACT: If you have a slow metabolism, you're more likely to gain weight

This is true, Allen says. Here’s why: If your metabolism is on the slower side, your body isn’t as quick to burn through the calories you’re consuming.

But your metabolism isn’t the only thing to consider when you’re trying to shed a few extra pounds. “Contrary to common belief, a slow metabolism is rarely the cause of excess weight gain,” according to the Mayo Clinic. “Although your metabolism influences your body’s basic energy needs, how much you eat and drink along with how much physical activity you get are the things that ultimately determine your weight.” In other words, even if you have a slow metabolism you can (thankfully) still control your weight by eating clean and working out.

MYTH: If you have a fast metabolism, you can eat whatever you want

Allen notes that people with a condition called Graves’ disease have overactive metabolisms and often lose weight even when they’re following an ordinary diet.

While it’s true that people with faster metabolisms don’t necessarily put weight on as quickly as those with slower metabolisms, a fast metabolism is not an excuse to throw traditional dietary advice out the window, Allen says. A balanced diet comes with seriously consequential health benefits unrelated to weight maintenance, including good heart health and the prevention of certain cancers.

FACT: Spicy foods boost your metabolism

Whether your preferred spice is chili pepper or ginger, “there is some interesting thought that they can boost the heat production in our bodies, leading to more calories being burned,” Allen says.

The effect is short-term, and how significant it is depends on “how hot the peppers are,” Allen says. “Lots of times, it’s uncomfortable,” she adds.

Adding just one tablespoon of chopped green or red chili pepper to your lunch or dinner could speed up your metabolism. Granted, the effect won’t last forever, but it could be worth that extra ingredient.

RELATED: 9 Foods That Boost Metabolism Naturally

MYTH: Eating multiple smaller meals throughout the day is better for your metabolism than eating three regular meals a day

“A lot of times we tell people to eat five or six small meals a day, but there’s some research coming out saying maybe it’s better to eat two or three modest meals a day. When people hear they can eat five or six small meals they’re not eating small meals,” Allen says. She explains that often people don’t keep track of just how much they’re consuming on any given day.

The bottom line on this one, she notes, is that you must be mindful of how much you’re eating and what you’re eating. Don’t think only in terms of calories, she warns. “It’s not necessarily a simple calorie equation. Are you eating a 250-calorie donut for a snack, or a 250-calorie protein and produce snack?”

MYTH: Supplements can speed up your metabolism

Over-the-counter products that claim to boost metabolism are bound to disappoint. “They don’t have energy or calories,” Allen says, adding that they’re not going to directly impact your metabolism. The potentially dangerous side effects of supplements have been well documented, and you should keep in mind that supplements don’t always play well with prescription drugs.

RELATED: 14 Ways to Boost Your Metabolism Right Now

FACT: Your metabolism slows down as you age

While this is a sad truth of aging, the news isn’t all bad: Your metabolism doesn’t hit a wall right when you turn 30, like some people might think. “You can control it a little bit,” Allen says, with the same lifestyle habits that always factor into the metabolism equation.

A slowing of your metabolism might be most noticeable around menopause in your 50s. “Once they go through menopause, [women] tend to have the most difficulty,” Allen explains. Hormonal changes that affect women when they go through menopause could increase their chances of putting on weight around their abdomens, hips, and thighs.

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