When you think of exercise for weight loss, do you think about long, sweaty workouts — or short, half-hour workouts? Exercise science has long held that if you want to burn more calories and shed fat weight, you need to put in some serious fitness time, whether you’re running, walking, or enjoying a Zumba workout. But a recent study questions that long-held assumption. A lot of ears — including mine — pricked up last month when the “lose weight with less exercise” headlines hit the media. Here’s what happened:
- Danish researchers recruited 61 healthy, sedentary and slightly overweight men in their 20s and 30s. They were randomized to a control group (no exercise), moderate exercise (~30 minutes/day), or high exercise (~60 minutes/day).
- Over the 13 weeks of the study, both exercise groups lost similar amounts of total weight and body fat. Surprisingly, those in the 60 minutes/day group had a negative energy balance (Calories burned vs. calories ingested) that was 20% less than expected. Even more surprising was the 83% higher negative energy balance in the 30 minutes/day group. These subjects were more physically active when they weren’t exercising.
- There were no statistically significant differences in calorie intake or non-exercise physical activity between the two groups that could account for the differences in negative energy balance.
- Rosenkilde M, Auerback P, Reichkendler MH, Ploug T, Stallknecht BM, Sjodin A, Body fat loss and compensatory mechanisms in response to different doses of aerobic exercise — a randomized controlled trial in overweight sedentary males, Am J Physiol Regul Integr Comp Physiol, 2012 Sep;303(6): R571-9. Epub 2012 Aug 1.