I like to consider myself a person with decent common sense.
But every so often I come across a bit of information that has me scratching my head.
First, let me ask you a question. Would you think that 60 minutes of exercise a day would cause you to lose more weight than 30 minutes a day?
It is simple logic, twice the exercise leads to twice the calories burned and therefore more weight loss.
But not so fast…
Some smart scientist from the University of Copenhagen decided to do a little test1.
The Exercise Study
The researchers found men living sedentary lifestyles and put them into three different exercise test groups.
Group one was assigned to do 30 minutes of aerobic exercise each day at a level of intensity high enough to produce a light sweat.
Group two was asked to do 60 minutes of aerobic exercise daily at the same intensity.
The final group was directed to remain inactive.
What do you think happened? Sure, it’s not hard to guess the group that remained inactive didn’t get very far with their weight-loss goals over the 13 weeks of the study.
But in the case of the two groups that exercised, do you think the one that exercised the longest lost the most weight during the study?
The Surprising Results
Well, the two active groups showed a significant – and surprising – difference in their results.
Group one, the men who exercised for just 30 minutes each day, lost an average of nearly eight pounds… great results.
But surprisingly, group two, the men who exercised for 60 minutes (twice the exercise time) lost only six pounds! This is two pounds less than the group that exercised for half as long. Where did my common sense go?
In case you were wondering, the group that exercised for 60 minutes did in fact burn twice as many calories during their exercise sessions as the 30-minute group. So the reason does not appear to be exercise intensity.
So how in the world did these results occur?
One interesting and little-reported piece of data from the study is that even though the group that exercised for 30 minutes lost more weight, both groups lost the same amount of fat (around eight and a half pounds).
At first this confused me until I thought at about it further.
Both groups actually lost more fat than total weight, meaning they actually added a bit of muscle (which is great news for both groups). A good way to know if you are losing weight the right way is when you are not also losing muscle mass.
Furthermore, it appears the 60-minute group put on more muscle than the 30-minute group. So in fact, they had better body composition results than the 30-minute group.
I know this can be confusing, so let’s do the math.
Total Pounds Lost = Total Fat Loss Minus (-) Total Muscle Gain.
Both groups had a Total Fat Loss of eight and a half pounds.
The 30-Minute Group lost a total of eight pounds, so in order to get eight and a half pounds of fat loss they had to gain around a half of a pound of muscle.
The 60-Minute Group lost a total of six pounds, so in order to get eight and a half pounds of fat loss they had to gain two and a half pounds of muscle. This is actually five times the muscle increase.
And this would be a good thing as more muscle fiber increases metabolism and is far more dense (and therefore smaller) than fat mass.
What Does This Really Mean?
I think the most important thing to remember is that both groups achieved excellent results compared to the sedentary group by any standards. So the real take home is to go out and get some exercise!
More specifically, I find that a lot of people don’t exercise because of time constraints, and this study clearly demonstrates the benefits of just 30 minutes a day.
Speaking of time constraints, in an earlier article I cover a very time efficient (and effective) form of exercising called high intensity interval training. If you haven’t read this already, you might want to take a look at it here.
I am curious as to what kind and duration of exercise you are doing, and what kind of results you are getting. So please share below, it will help everyone out. And if you have any unique insights, questions, or advice to the group… please share below.
Steven Sisskind, M.D.
1. M. Rosenkilde, P. L. Auerbach, M. H. Reichkendler, T. Ploug, B. M. Stallknecht, A. Sjodin. Body fat loss and compensatory mechanisms in response to different doses of aerobic exercise – a randomized controlled trial in overweight sedentary males. AJP: Regulatory, Integrative and Comparative Physiology, 2012;