how long has this been goin’ on?
intensity vs. duration

by Dave Harney

Duration vs. Intensity. Sounds like some type of electromagnetic techno jargon. But not in this case. Here it refers to the effect of exercise on the metabolism. When it comes to dieting, many believe it’s the intensity of your workout that will make a difference in whether you lose weight or not. But very often it has to do with HOW LONG you work out, not how hard.

It is estimated that as many as 65% of Americans are overweight. It is possible that nearly all of them would tell you they are trying to lose weight. If they are making a serious attempt to do so, it is likely they are also exercising. After all, one must spend more calories than one consumes in order to implement an effective weight loss program. Exercise is an excellent way to spend those excess calories.

What then, is the best amount of exercise for long-term weight loss?

In a 2003 study published in the Journal of the American Medical Association, Dr. John Jakicic and his colleagues from the University of Pittsburgh Physical Activity and Weight Management Research Center asked this question in a 12-month study examining the effect of different lengths and intensities of workouts in a group of 184 sedentary, overweight women. These women were put into 4 groups:

1. vigorous intensity/high duration
2. moderate intensity/high duration
3. moderate intensity/moderate duration
4. vigorous intensity/moderate duration.

Intensity was determined by the amount of energy expenditure during exercise. The women were also asked to reduce their calorie intake to between 1200 and 1500 calories a day with no more than a 20-30% fat component. After 12 months in this program all the exercise groups tallied a weight loss. Somewhat surprisingly, there was no difference between the groups who exercised vigorously and those who only engaged in moderate exercise.

The same was true for cardiorespiratory fitness levels. All groups improved, and there was no difference in whether they engaged in the moderate or vigorous program. Finally, and perhaps most interestingly, it was the women who engaged in longer exercise durations that recorded the greatest weight loss. Specifically, the group that exercised;

1. less than 150 minutes per week recorded an average weight loss of 4.7%.
2. 150-200 minutes per week recorded an average weight loss of 9.5%
3. 200 minutes per week recorded an average weight loss of 14%.

The researchers concluded that weight loss programs utilizing exercise should try to maintain at least 150 minutes per week of moderate intensity exercise, and when appropriate, an increase to 60 minutes per day. But recommendations differ. For example, the American College of Sports Medicine suggests a minimum of 30 minutes of moderate-intensity activity (150 minutes per week), to improve health. Other groups, like the Institute of Medicine recommend a minimum of 60 minutes per day of exercise on most days of the week to control body weight.

The bottom line: Get out there and exercise. No matter what or how long, your body will thank you for it!