For Weight Loss, Less Exercise May Be MorePosted: September 19, 2012
From the NYTimes;
Most people who start working out in hopes of shedding pounds wind up disappointed, a lamentable circumstance familiar to both exercisers and scientists. Multiple studies, many of them covered in this column, have found that without major changes to diet, exercise typically results in only modest weight loss at best (although it generally makes people much healthier). Quite a few exercisers lose no weight. Some gain.
But there is encouraging news about physical activity and weight loss in anew study by researchers at the University of Copenhagen. 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.
To reach that conclusion, the Danish scientists rounded up a group of pudgy and sedentary young men, a segment of the population increasingly common in Denmark, as elsewhere in the world. The volunteers, most in their 20s or early 30s, visited the scientists’ lab to undergo baseline measurements of their aerobic fitness, body fat, metabolic rates and general health. None had diabetes, high blood pressure or heart disease and, while heavy, they were not obese.
The men were then randomly assigned to exercise or not. The non-exercisers, who served as controls, returned to their former routines, with no change to their diets or sedentary ways.
A second group began 13 weeks of almost daily moderate workouts, consisting of jogging, cycling or otherwise sweating for about 30 minutes, or until each man had burned 300 calories (based on his individual metabolic rate).
A third group tackled a more strenuous routine of almost hour-long workouts, during which each man burned 600 calories.
The men were asked not to consciously change their diets, either by eating more or less, and to keep detailed daily food diaries throughout the 13 weeks.
On certain designated days, they also were asked to don sophisticated motion sensors that would measure how active they were in the hours before and after exercise.
At the end of the 13 weeks, the members of the control group weighed the same as they had at the start, and their body fat percentages were unchanged, which is hardly surprising.
On the other hand, the men who had exercised the most, working out for 60 minutes a day, had managed to drop some flab, losing an average of five pounds each. The scientists calculated that that weight loss, while by no means negligible, was still about 20 percent less than would have been expected given the number of calories the men were expending each day during exercise, if food intake and other aspects of their life had held steady.
Meanwhile, the volunteers who’d worked out for only 30 minutes a day did considerably better, shedding about seven pounds each, a total that, given the smaller number of calories that they were burning during exercise, represents a hefty 83 percent “bonus” beyond what would have been expected, says Mads Rosenkilde, a Ph.D. candidate at the University of Copenhagen who led the study.