Is THIS Responsible for Your Weight Creep?

Whenever experts talk about increasing obesity rates, they tend to lay the blame on our crappy diets: too much sugar, junk food, drive-thru meals; you know the story. But the research team behind a new study to be published in the American Journal of Medicine makes the case for a different conclusion: It’s not what we’re eating too much of that’s making our jeans feel tighter, they suggest, but how little exercise we’re actually getting.

Study authors looked at data from the National Health and Nutrition Examination Survey, comparing stats from 1988 to 1994 with numbers from 2009-2010, based on interviews and examinations of about 20,000 adults. In that time, the average BMI and waist circumference increased in all demographic groups, with young women between 18 and 39 scoring the biggest jump in obesity rates. And while there was no recorded surge in the average number of calories consumed, the researchers did find a substantial change in the amount of exercise study subjects took part in—with 52 percent of women reporting zero leisure-time physical activity, up from 19 percent between 1988 and 1994. Using this data, study authors were able to correlate higher rates of obesity with a sedentary lifestyle.

MORE: 8 Totally Honest, No-B.S. Truths About Trying to Lose Weight

Keep in mind that the study had its limitations. First, researchers didn’t follow the same people from 1988 to 2010 but instead used samples meant to represent the U.S. population. Also, the lead author raised the possibility that people in the self-reported survey may have underestimated their calorie intake. Additionally, this finding is pretty much the exact opposite of previous findings on similar topics (namely, that diet is typically more effective than exercise at keeping off the pounds; "abs are made in the kitchen," and all that.) Finally, correlation isn’t causation—in other words, the study doesn’t prove that too little exercise is the reason our BMIs are higher than ever, on average. Still, the research serves as a good reminder that being active—whether it’s through cardio class, a leisurely hike, or just using the stairs instead of the elevator at work—is crucial when it comes to keeping excess pounds from creeping on. Find out how to motivate yourself to move, even when you’re totally not feeling it. 

MORE: Bored with Running? 6 Ways to Bust Out of Your Rut 

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