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Roy Stevenson Wednesday, 28 December 2011 07:44 TWEET COMMENTS 4

Weight Station - Page 3

"Besides burning calories, running helps control my weight in that if I'm training for a particular race, I'm motivated to eat sensibly, for example, by including more vegetables. If there's no racing goal on my horizon, I tend to eat more junk food and put on weight," says Crowther.

Because of the disappointingly modest number of calories burned during one running session at a moderate pace, we must therefore run consistently enough to cause an overall calorie deficit—several days a week.

For this reason, most researchers consider aerobic exercise a weak method for accelerating weight loss. A one-year study at Stanford University (King et al 1991) found that 350 men and women, who did three to five exercise sessions lasting 30 to 40 minutes each, had no significant weight loss (although their aerobic fitness improved from five to eight percent).

So to burn substantial numbers of calories for weight loss we need to run at least one hour per day, six or seven days per week, at a fast clip; if you ask prototypical thin distance runners about their training, you will find they run close to this amount and pace. A caveat here: beware of overeating because you are hungry from your running program—this will negate the effects of the calories you have burned while running.

Running in the So-Called "Fat-Burning Zone"

What about the fat-burning-zone theory—i.e. work out long and slow to burn fat calories—that is so popular these days? This theory posits that when we run at a nice slow pace for a long time we tend to burn fat as our primary fuel source.

While running at low intensity does tend to draw more from fatty acids than from carbohydrates, the reality is that whether we burn fats from long, slow running or glycogen from shorter, high-intensity sessions, when it comes to losing weight, our body ultimately only cares about how many calories we have burned in a workout, not what fuel we burned.

Some research shows we may be better off exercising at a higher intensity for a shorter period of time, rather than exercising at a lower intensity for a longer period of time, because we will burn more calories in that scenario. Vigorous exercise also has another health benefit, according to some studies—it tends to preferentially draw fat from the abdominal area once glycogen stores start to deplete.

The Running "After-Burn"

What about the theory that our resting metabolism is revved up after running and that we burn as many calories after we run as we do during the training effort? Well-researched studies show that the "post-running calorie burn" is minimal.

Here is an example: Jogging at 12-minutes per mile for 30 minutes causes resting metabolic rate to stay elevated for 20 to 30 minutes, and only burns 12 additional calories post-run. When running intensity is increased to 75 percent of aerobic capacity for 35 to 45 minutes, we burn an extra 15 to 30 calories. Hardly earth-shaking figures when you consider that we need to burn 3500 calories to lose one pound of fat.

What about really long runs? Studies on extended running for 80 minutes or longer also found a very modest after-running calorie burn. Weighing these not-so-impressive after-run burns against the calories in one Hershey's kiss (25 calories) is a great reality check.


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