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Good Housekeeping

THE SCIENCE OF METABOLISM

THE BASICS

So What Is Metabolism, Anyway?

Think of it as the engine within your cells that keeps you going. A car runs on gas; you run on calories, which are units of energy. Most of these calories are burned through your body simply doing its job existing: fueling your cells and keeping your heart pumping, your blood circulating, your lungs breathing, your digestive system working and your brain neurons firing (in fact, your brain alone needs about 420 calories a day just to keep functioning). You’re always incinerating calories, even while asleep.

Here’s how it works:

1) You eat food.

2) Your body breaks it down into its simplest forms of carbohydrates, protein and fat.

3) The calories in those components are converted to energy, used by your cells and tissues to grow and repair themselves.

We know what you really want to know: Is there a way to burn more — that is, to get a faster metabolism? The answer is yes. It begins with what you eat and how you move — more on these two coming up. Other factors:

Genetics: You may have a naturally faster or slower metabolism, though lifestyle still has a big impact.

How stressed you are: Long-term stress releases hormones that screw with your digestion so your food isn’t used as efficiently.

How well you sleep: This is critical. When your body is shortchanged on zzz’s, it’s pushed into conservation mode, so you burn fewer calories.

Eat to Burn

It’s lunchtime! As your body breaks down your meal, your brain gets feedback signals — from the nutrients, your hormones and how much you’re moving around — and “decides” whether to use the calories right then or store them. This is what affects your metabolic rate:

HOW MUCH YOU EAT. Consistently take in more calories than you need, and a lot of what isn’t used gets stored as fat.

WHEN YOU EAT. Chowing down every three to four hours keeps your metabolism chugging. There may also be an advantage to front-loading calories: People who skip breakfast tend to have a surge of the hunger-boosting hormone ghrelin in the p.m., so they munch before bed. This can disrupt sleep, which messes with your metabolism.

WHAT YOU EAT. Skip low-nutrient simple carbs. They’re digested so quickly that they set off a cascade of metabolic reactions that soon leaves you hungry again. You eat more overall — hello, lbs! Down a combo of fibrous complex carbs and protein, which will keep you full so you’ll eat less.

CAN FOODS MELT FAT?

If you believe what you see online, you probably think there are loads of miracle eats that eradicate pudge. If only! The real deal…

TURMERIC AND SPICY FOODS

Compounds in turmeric have been linked to reduced risk of chronic inflammation, which is connected to obesity. But (sorry) more turmeric doesn’t rev your metabolism. As for spicy foods, some research has tied the capsaicin found in hot peppers to an increased metabolic rate; it also may help mobilize fat cells to be used for energy. But you’d need to eat a ton: In one study, people who took a daily capsaicin supplement for 12 weeks lost less than a pound.

WATER WITH LEMON

Sipping a very hot or very cold beverage may help raise metabolism — but the impact lasts only about 30 to 40 minutes after drinking it. That said, being well hydrated is crucial for maintaining a healthy weight; if adding some lemon helps you do that, go for it.

TEA AND COFFEE

A few small studies have linked a speedier metabolism to certain teas (especially green and black) and caffeinated coffee. The effect apparently comes from the combo of caffeine and flavonoids (antioxidant-like compounds); the modest benefit seems to kick in once you’ve had at least four cups in a day. However, because sleep is also key to a swifter metabolism, you’ll want to find a balance.

Turmeric and water: Westend61/Getty Images. Cucumbers: LOVE_LIFE/Getty Images. Coffee: Igor Golovniov/Getty Images.

“NEGATIVE CALORIE” FOODS

This is not a thing, although we wish it were. There’s no scientific basis to the long-standing perception that some foods — like celery and sugar-free gum — boost metabolism because they’re low in calories and require so much chewing that you actually burn more cals than you eat.

OF THE CALORIES YOU TORCH…

60%-75% are expended to fuel hardworking organs like the brain, heart and lungs

15%-30% are used as you move, whether that’s at Zumba or while vacuuming

10% are burned by the process of digesting your food and drink

THE FITNESS FACTOR

Moves that f ire up your metabolism

There are so many reasons to exercise — it’s super-important for your heart, brain, bones and immune system. And the more you move, the more calories you’ll burn. But exercise will not zero out a high-calorie, bad-quality diet — you just won’t burn enough. For weight control, follow the advice in “Eat to Burn” (previous page). What exercising can do: make your metabolism speedier by increasing your levels of testosterone and growth hormone. So kick it up with a three-pronged approach:

CARDIO

Doing intervals can be especially effective at raising your metabolic rate and burning fat. It can also produce an afterburn, meaning you’ll continue to zap cals after exercising. To do an interval workout, alternate steady movement (say, a brisk walk) with faster movement (a moderate jog). Aim for 20 to 30 minutes at least three times a week.

STRENGTH TRAINING

Building muscle revs your metabolism. The why: Even at rest, muscle burns four times as many calories as fat, so the more muscle you have, the more you’ll burn. (That’s why men tend to have faster metabolisms — more muscle!) Do at least two weight workouts per week.

Woman: RoBeDeRo/Getty Images.

“NEAT” MOVEMENT

That’s “nonexercise activity thermogenesis”: the calories expended by fidgeting during a meeting or running to the water fountain. In one study, those who did lots of NEAT movement burned as much as 2,000 cals more a day! So stroll when you’re on the phone; hit a museum rather than a movie; go to the store instead of ordering online.

JILLIAN MICHAELS’S

Fast Blast

By incorporating nearly every muscle group in the body, this dynamic, explosive exercise burns more calories while you do it and long after your workout is over.

LONG JUMP WITH CRAWL BACK

1. Start standing with feet hip-width apart.

2. Perform long jump: Bend knees and, swinging arms, take off as far forward as you can, landing on both feet (A).

3. Hinge at hips to place both hands on floor.

4. Jump back into plank position, with arms straight under shoulders and abs tight.

5. Walk hands backward toward feet (B), keeping legs as straight as possible and lifting tailbone toward the ceiling. Stand and repeat for 30 seconds. Do three sets.

WORK OUT WITH JILLIAN’S APP

Skip the gym — use your smartphone instead! Jillian’s personalized fitness app makes it easy to tone up at home. Good Housekeeping readers get a special 10% off at jillianmichaels.com/gh.

THE SCIENCE OF…

Experts On Call

ELAINE CHIN, M.D.

Founder and chief medical officer of Executive Health Centre in Toronto, Canada

WILLIAM HOWATT, PH.D.

Behavioral scientist and expert in mental health and coping skills

Jillian Michaels: My Fitness App. London: Mike Garten.

JACLYN LONDON, M.S., R.D.

Nutrition director of the Good Housekeeping Institute

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