Exercise for Weight Loss? Not Much Is Better Than Lots…

Some additional research on the exercise front, this time out of the University of Copenhagen. In the paper, “Body fat loss and compensatory mechanisms in response to different doses of aerobic exercise–a randomized controlled trial in overweight sedentary males” (American Journal of Physiology), researchers assert that:

Although well recognized as an important means for weight loss maintenance (9), the role of habitual endurance training in weight loss is scrutinized, and it has been suggested that exercise leads to compensatory responses. In the current study, we show that despite that one group undertook twice the amount of endurance training, the reduction in body weight and, more importantly, in body fat was the same as the weight loss and was equal among the two groups (a healthy weight loss). Surprisingly, the reduction with the moderate-dose exercise was far greater than what could be explained by the increased energy expenditure from the training itself (no compensation).

Again, the group that did 2x the amount of exercise wound up losing the same as the group that did less. But if you did nothing, you didn’t lose as much. Sound confusing? Gretchen Reynolds sums it up nicely in her New York Times article, “It found that exercise does seem to contribute to waist-tightening, provided that the amount of exercise is neither too little nor, more strikingly, too much.”

The researchers speculate that one of the reasons the people who exercised the most didn’t lose as much weight is that they tended to move less when not working out, as if they were fatigued…so over the course of the day, they burned fewer calories. This is oft speculated to be a reason for the exercise/weight loss paradox.

On a semi-related note, I’m working my way through Phinney and Volek’s, The Art And Science of Low Carbohydrate Performance again, and in that, they do a quick survey of the literature related to how exercise tends to REDUCE resting energy expenditure. In it, they write,

There are 4 well-controlled, inpatient, metabolic ward studies (the gold standard for human research) published from 1982 thru 1997 that showed statistically significant reductions in resting metabolic rate when overweight subjects performed 300-600 Calories per day of endurance exercise for weeks at a time[28-31]. There are no equally rigorous human studies showing the opposite. There are animal (rat) studies that show the opposite, and there are human studies done under less controlled conditions that show the opposite. However there are also similarly less rigorous studies that agree with the above four gold-standard studies. (39)

So is this a possible explanation for the results of the Copenhagen study? Perhaps. While the results are interesting, at the end of the day, it still does not appear that exercise is that much of a contributor to weight loss. While it does have an effect, I’ll still maintain that diet is the primary agent involved in shedding weight.

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