Staying Alive / The myth of the 1,000-calorie workout

"Burns up to 1,000 calories per workout."

You’ve seen the claim attached to AirFit, running, TurboKick, Zumba, kickboxing, GravityFit, the Original Boot Camp, and boxing—and that’s just in the first two pages of a Google search.  Burning 1,000 calories sounds pretty awesome; that’s nearly a third of a pound (a pound equals 3,500 calories) per workout.  At that rate, you’ll be back in your skinny jeans by summer. Heck, you might even have to buy skinniER jeans.

Not so fast. While any of the above exercises are great ways to burn calories and increase cardiovascular fitness, believing the 1,000-calorie claim—and eating accordingly—will have you buying new jeans all right, but in a larger size.

Until my heart rate monitor died, I used to wear it for every workout, and no matter how tough the workout—including the aforementioned running, kickboxing, Boot Camp, etc.—I never burned more than 600 calories an hour, and that was for the toughest, nonstop, sweating-from-the-shins, dripping workout.  Most often, an hour of cardio was in the 500-calorie-an-hour range.  Keeping in mind that most gym classes are less than an hour—forty to fifty minutes is a more realistic range—it becomes clear that while "up to 1,000" an hour may be true, it’s not going to be true for you. Even if you do a full hour, and calorie burn varies from person to person, it’s still the very, very, very rare person who might reach that peak. In fact, if you go to websites that list calories burned for various exercises—sites that have no vested interest in whether or not you buy a DVD or come to a class—the numbers come nowhere near this 1,000 range (Zumba, for example, is cited as burning 400 to 700 an hour, and running up to 600).

Here’s why

Tests on these workouts are frequently conducted during a short, intense portion; i.e., if the hardest part of the workout is a five-minute burst that burns eighty-four calories, simple math would dictate that the entire workout would then burn 1,000 calories. Except that no workout maintains that intensity for the duration of the workout; most of us couldn’t keep up.  Look closely at the calorie estimations on fitness sites: they nearly always say something along the lines of "at maximum intensity" or "continuous." Now think about your last Zumba class—did you rest between songs? Last time you jumped in the pool to swim laps, did you switch to breast stroke and slow down every so often? And, most importantly, did your cardio session stop short of an hour? If you answered yes to any of these questions, it’s a sure bet you didn’t burn 1,000 calories, and, in fact, probably burned closer to forty percent or more less than that.

So how many?

Fitness is not an exact science but the number of calories you do actually burn will depend on several factors:

1) Gender: You know how jealous you get when you and your mate each decide to lose fifteen pounds, and he’s boasting about five-pound-a-week losses, while you dutifully record pitiful half-pound increments? Men lose weight faster than women because they burn ten to fifteen percent more calories than woman during any given activity. This is partially because they naturally have a higher percentage of muscle mass, which, if they start weight training, becomes an even higher percentage at a quicker rate than it can for women. Estimates are that in the first year of weight training, men typically put on ten to fifteen pounds of muscle, while women come in at just four to six with the same effort. (That simple fact neatly puts to rest all those claims you hear about "fat turning to muscle" after a month or two of exercise and eating well.)

2) Current body composition: Closely related to the above is the amount of muscle you do have. Muscles burn more calories than fat just to stay alive, so it stands to reason that the more muscle you have, the more calories you will burn per workout.

3) Age: Both ability to burn calories (metabolism) and ability to gain muscle decrease with age. With the exact same workout, a twenty-five-year-old will burn more than the forty-five-year-old every time, which is why it was so much easier to lose weight when you were younger, and why it is so important to weight train as you get older.

4) Current weight: If you’ve ever been on a calorie-deficit diet, such as Weight Watchers, you know that the more you weigh, the more you’re allowed to eat and, as you lose, your daily allowable caloric intake is decreased. That’s because the more you weigh, the more calories you burn—both at rest, and during a workout. Biggest Losers contestants can burn a lot more calories in a workout than someone of lesser size.

5) Genetics: You’ve no doubt witnessed the unfair fact that some people just burn calories faster.

6) Intensity: What I said up top: the harder you work, the more calories you will burn.

Of these factors, gender, genetics, and age are out of your control. So is your current weight, because gaining weight in order to burn more calories is counterproductive. You can weight train to optimize your body composition, which will, in turn, burn more calories, but even that isn’t going to get you closer to the 1,000-calorie-an-hour results you want, especially if you’re a woman. So here’s the hard truth if you haven’t figured it out already: you have to do hard work to burn a ton of calories.

Top calorie burners

So, which exercises burn the most? All of the ones making the crazy claims are in the top echelon, and you can’t go wrong with any of them. High Intensity Interval Training (HIIT) can burn the most calories in the shortest amount of time, if you’re truly working the intervals at an anaerobic capacity. I’ve always found it easiest to drop weight with running, because when you’re running, you really can’t rest; even jogging burns nearly as many calories because it’s still non-stop. Circuit training, which is any routine where you go from one exercise to another without rest—cardio intervals alternated with weighted exercises, for example—is also a high calorie burner.  

Bear in mind, however, that the difference between a grueling, nonstop workout, and a fun, lower intensity workout that you might enjoy more isn’t going to be enough to let you eat whatever you want. In fact, if you love the lower intensity activity enough to actually continue it for an hour as opposed to quitting from exhaustion, it’s probably going to be a wash. After my heart rate monitor died, I didn’t get a new one, because a) the numbers aren’t foolproof, b) how you feel working out is the most important thing, and c) once you know the number, it’s hard not to think about it as it relates to what you can eat; i.e., the focus is on the calories in the food and not the food choice itself.

In the end, weight maintenance like so many other things in life relies on the eighty/twenty rule: it’s eighty percent what you eat and twenty percent exercise. So eat well, burn calories doing what you like, and remember there are no magic pills, bullets, or 1,000-calorie-an-hour workouts.        

For more on Health and Fitness check out:

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Staying Alive / A fit mind

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Donna Hoke is a frequent contributor to Spree.