Tuesday, July 29, 2008

Is Exercise Necessary for Weight Maintenance?

Yes, but the much more important question really is why?

Today a new paper in the Archives of Internal Medicine again suggests that exercise is crucial for long term weight maintenance, but I think misses the boat on why.

The paper, written by one of the giants in exercise and its role in obesity treatment and prevention Dr. John Jakicic and colleagues, follows 201 women for 24 months randomizing them into one of 4 different exercise arms (having to do with intensity and duration) and giving all of them Calorie reduced diets.

They then subdivided the results into groups representing percentages of maintained weight loss at 24 months and analyzed scads of data.

Their results and conclusions?

The folks who maintained a weight loss of greater than 10% of their starting weights exercised more minutes per week than those who did not. The authors concluded that the magic number of weekly exercise minutes for weight maintenance therefore were 275 (an average then of 40 minutes daily or an hour 5 days a week).

The thing is, I don't think that's the whole story.

Looking more carefully at the data we can see that on a weekly basis the folks who exercised the most burned only 1,145 more Calories than the folks who exercised the least (illustrating that exercise really doesn't burn boatloads of Calories given that to burn those additional Calories those folks on average exercised 3.5 hours more a week). That's only an average of 163 Calories more burned daily - not much to write home about.

No, for me the story is elsewhere in the data.

Looking at those who exercised the most, on a daily basis they were consuming 444 Calories less than those exercising the least. Extrapolating that and those folks were eating 3,108 fewer Calories a week! That's almost a full pound of Calories less a week! They also had much better scores on an eating behaviour inventory meant to assess weight control eating behaviours.

Translation?

The folks who exercised the most, ate the least and controlled their eating the best and in fact the magnitude of their dietary interventions at 24 months were 3 fold higher in Caloric impact than their exercise interventions.

My conclusion?

Exercise works and is integral to most for weight maintenance, but not via its direct Calorie burning capacity (which is small), but rather through its remarkable ability to cultivate healthy attitudes about weight management and in so doing, support dietary restraint and thoughtfulness for the long run.

Therefore to truly harness the power of exercise, we need to explore how exercise leads these folks to consume less Calories and stick to weight control eating behaviours. If we can figure that out, perhaps we can create interventions that do not in fact necessitate seemingly other-worldly amounts of daily exercise.

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