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Tweaking Exercise Guidelines ; Diet, Metabolism Must Be Factored In

Posted on: Tuesday, 22 February 2005, 15:00 CST

The government's new physical activity guidelines include one curiosity that's been largely overlooked: the recommendation that people trying to lose weight get 60 minutes of exercise per day while those trying to maintain weight loss clock 90 minutes daily. So maintaining weight loss requires more exercise than achieving it? What gives?

(The guidelines recommend 30 minutes of daily exercise for people who are relatively fit and not in the above categories.)

First, some good news for the 60-minute crowd, which is to say the majority of U.S. adults: You might get away with less. Russell Pate, a University of South Carolina kinesiology professor who served on the Dietary Guidelines Advisory Committee, said, "When we drafted these guidelines, we said 'as much as 60 minutes per day' based on our review of existing evidence." The final version, which Pate said he was not asked to review, simply stated "60 minutes."

"I do not support that," he said. Variances in individuals' diets and basal metabolic rates [energy consumption at rest] affect how much exercise is needed to lose weight. "Activity is a major part of it, but those other factors are very significant as well." Pate cites research showing that many overweight people exercise 30 minutes a day and don't shed weight.

"If you are meeting the 30-minutes-a-day recommendation and not losing weight, you should increase your amount of exercise" and focus on diet and other aspects of your lifestyle, Pate advises.

As for the apoplexy-generating 90-minute recommendation for those trying to keep weight off: That's based on data from the National Weight Control Registry, a continuing study of about 3,000 people who have lost a significant amount of weight and kept it off. The registry shows that people who sustain substantial weight loss get, on average, 90 minutes of moderate-intensity activity every day.

Do they need all that if they've already dropped the pounds? Harold Kohl, an epidemiologist at the Centers for Disease Control and Prevention, explained that the formerly overweight body, which had grown accustomed to higher-than-needed caloric input, still acts as if it needs the extra calories. And even people who resist the urge to overeat struggle because the metabolism slows to meet what it perceives as a calorie deficiency. So the individual must work that much harder to burn energy.

"Moderate intensity" equates to brisk walking - at roughly three to four miles per hour - or applying similar exertion to cycling, swimming or other activities. The "vigorous" range begins with jogging and includes spin-cycling, running full-court basketball, cross-country skiing, a competitive racquetball match, etc.

Shorter, high-intensity workouts burn as much energy as longer, less-intense workouts. Example: If you run hard and cover a mile in seven minutes, you burn about the same amount of energy as you would walking that mile in 20 minutes or jogging it in 10. So, if you're in shape to handle it, you could blow through your government-issue 30- to 60-minute workout in 20 or 30 minutes at higher intensity.

Source: Record, The; Bergen County, N.J.

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