Science Friday – Exercise is Not an Excuse to Eat Like Crap
While the efficacy of exercise on health measurements is well established, there is still quite a bit of debate in the literature regarding the effectiveness of exercise alone to improve body composition. So if you bust your butt in the gym, but keep your crappy diet, what kind of results should you expect? This is the question the STRRIDE study entitled “Effects of the Amount of Exercise on Body Weight, Body Composition, and Measures of Central Obesity” seeks to answer.
In this study 182 individuals were randomly assigned to one of four exercise groups:
- High Amount/High Intensity
- Low Amount/High Intensity
- Low Amount/Low Intensity
- Control
The exercise amount was set by the calories/kg/wk burned and the intensity was determined by the oxygen consumption (%VO2max). The exercises were varied between stationary bike, treadmill and elliptical. Note that these individuals were counseled to not make any changes to their total caloric intake nor to their macronutrient breakdown. They were told from the beginning that this was an exercise study and not a weight loss study. The results from this 9 month exercise intervention are shown below:
The results clearly show that the control group gained body fat while the exercise groups lost body fat. Not surprisingly the high intensity groups lost more body fat than the moderate intensity group. This study also showed that increasing the exercise dose led to better fat loss since the High Amount group out-performed both Low Amount groups. The conclusion the authors draw is certainly valid – namely that exercise will help individuals maintain and even lose weight without any corresponding dietary changes.
But if we dig into the numbers a little bit, we see that maybe things aren’t quite so great. Remember this was a 9 month study and the individuals involved were not very lean to begin with; even after the fat loss they were still ~30% body fat. So should we really celebrate the fact that after 9 months of exercise these people lost ~4-6 lbs of fat? Don’t get me wrong, losing any fat is great but that’s a lot of work for 5lbs if you ask me. Sure the High Amount group lost about 11lbs but they were exercising quite a bit – the equivalent of running 20 mi/wk. Are you training that much at high intensity? Consistently?
Therein lies the problem with increasing your exercise level w/o changing your diet. Many individuals will simply compensate by eating more than they would have otherwise. Whether that is a physiological or psychological response really doesn’t matter – it seems to be a real effect. The good news is exercise alone is better than diet alone, and I’ll have some studies on this in future posts, because the majority of people gain their weight back if they only address their diet and do not increase their exercise dose. Weight Watchers anyone?
The real magic starts to happen when you increase your exercise AND improve your diet. The old saying is true “you can’t outwork a crappy diet.” So if you’re exercising 3-5x/wk, and hopefully you’re doing high intensity training, then that’s a great start but don’t be surprised if you don’t see massive changes in your body composition. I’ll have some future posts on different types of dietary changes but the most important thing is to understand that it’s a lifestyle change. You can’t eat a can of green beans for lunch the rest of your life, but you probably can do without the pasta and beer 3+ nights/wk…