FACT or FICTION? Keeping your heart rate in the fat-burning zone (60-70% of your max heart rate) helps to shed fat faster…?
Myth: Exercise done at a low intensity, such as walking, is better at fat burning than other high-intensity activities, like running or cardio activities where you push yourself very hard.
The Truth: In a strict scientific sense, these claims are true because working at a lower intensity requires less quick energy and a higher percentage of fat is burned. But you’ll also burn fewer calories than you would if, for the same amount of time, you work out at a harder intensity (running versus walking). Although it’s technically true that exercising in the so-called “fat burning zone” (at a lower intensity level of about 60% to 70% of maximum heart rate) does use a higher percentage of fat calories for fuel, the overall total calories burned is still lower. The reason is simple. Fat is a slow-burning fuel that requires oxygen to convert it to a usable energy, so it’s great for long, steady, slow exercise, like backpacking, or cycling a long distance. Most people have enough stored body fat to fuel low level activity for days and days without running out of energy, but if you want to go fast, work all-out, or burn the most calories per minute, you need to rely on the faster-burning carbohydrate (glycogen) for energy. Converting fat to fuel takes longer, and requires lots of oxygen. In the strictest definition, this is called aerobic metabolism.
For almost two decades, we’ve been hearing the seductive call of the “fat-burning zone,” in which you burn a greater percentage of fat calories. And, we’ve been told, you get there by doing moderate—not hard—exercise.
Turns out, it’s not that simple. The catch? When you exercise at 60 to 70 percent of your maximum heart rate, in that so-called “zone,” you burn fewer calories per minute during and after your workout. To crank your metabolism, you need to push your body harder—a lot harder.
The Exertion Scale
Picture your activity level on a spectrum. On one end is the effortless kind, like sitting at your desk or walking to a meeting. “When you’re not exerting yourself, your body actually burns a higher percentage of calories from fat than it does when you’re active,” says Alex Koch, Ph.D., an associate professor of health and exercise sciences at Truman State University in Missouri. That’s partly why the “fat-burning zone” was so appealing—it sounds awesome. But of course that doesn’t mean sitting at your desk or wandering the halls at work will shrink your hips faster than doing jumping jacks or running a sprint will. “You’re maybe burning one to two calories a minute,” Koch explains, “which doesn’t add up to a lot of fat.”
Toward the other end of the activity spectrum is a super intense workout that sends your heart rate way beyond the classic fat-burning zone. At this point, your body needs quick energy, so it starts burning less flab and turns instead to carbohydrates, which enter the bloodstream faster than fat does. The upside: The harder you work, the more calories you burn. “At your max effort, you could be burning 20 to 30 calories a minute, “Koch says. And more calories burned, of course, equals more pounds lost.
In fact, research shows that the harder you go, the better. “Besides burning more calories per minute, high-intensity exercise—such as intervals, in which you alternate between short, hard efforts and easy periods or complete rest—unleashes a flood of hormones, including epinephrine, which helps your body burn calories even when you’re not working out,” Koch says. For example, people who cycled at a high intensity for 20 minutes torched more calories for hours after their workouts than they did after cycling at a low intensity for 30 to 60 minutes, according to a study reported in Medicine & Science in Sports & Exercise. “Exercising in the classic fat-burning zone doesn’t offer these benefits,” he says.
The New Fat-Burning Zone
That doesn’t mean light-to moderate-intensity exercise is out of the picture. Mellow efforts can still be part of your workout: As a warm-up or cool down, they ease your body into and out of an intense session. They also reduce stress, amp up your cardiovascular health, increase bone density, and, of course, burn off some calories.
However, to fry flab faster, follow the principles of interval training or HIIT (high intensity interval training) You’ll know you’re in the zone when you combine short bursts of activity that require you to breathe so hard you can’t utter a word, followed by easier efforts that let you catch your breath. This new fat-burning zone isn’t really a single zone at all. It’s more like a cocktail of efforts that, when mixed together the right way, delivers a mega calorie crush to reveal a slimmer physique. Classes Such as Zuu, Func or TRX are a classic example of interval training and ensure your heart rate sores up and down
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