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As of September 2017, new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Check out my bestselling new book on the science of endurance, ENDURE: Mind, Body, and the Curiously Elastic Limits of Human Performance, published in February 2018 with a foreword by Malcolm Gladwell.
- Alex Hutchinson (@sweatscience)
Fitness or fatness: which is more important in determining your health? As I discussed in this Jockology article, some researchers (most notably Steven Blair at the University of South Carolina) believe that most of the health problems we associate with obesity are actually a consequence of poor aerobic fitness. In other words, they argue, it’s okay to be a little portly as long as you’ve exercised enough to have good endurance.
This challenges the basic tenet of old-school, keep-it-simple nutritional thought — that good health is simply a matter of matching the calories you eat to the calories you burn. Can your body tell the difference between a calorie burned through exercise and a calorie avoided through dieting? Well, a really interesting and excruciatingly careful study from researchers at Louisiana State University has just tackled this question.
Here’s the gist: 36 moderately overweight subjects, divided into three groups. One group was the control, and stayed exactly the same during the six-month study. A second group cut their calorie intake by 25 percent, while the third group cut calories by 12.5 percent and increased calories burned through physical activity by 12.5 percent.
As expected, the two intervention group lost exactly the same amount of weight (about 10 percent of their total), and they both shed roughly the same amounts of total fat and visceral fat. This makes sense, because they were both operating under identical calories deficits. Here’s the rub, though: only the exercise group had significant improvements in insulin sensitivity, LDL cholesterol and diastolic blood pressure.
This tells us that a calorie is not just a calorie — it matters how you cut calories. And, as Steven Blair is constantly pointing out, being thin is no guarantee of health if you’re not active. (And, as a nice bonus, it also tells us that it’s possible to drop 10 percent of body mass through a combination of diet and exercise — though it probably helps to have a team of researchers cooking your meals and supervising your exercise!)