There’s good news and there’s bad news in the fight against obesity. Several studies show that Americans consume fewer calories than they did 10 years ago, and they also eat less junk food. That should be reason to celebrate, except that the decline in caloric consumption hasn’t led to a decline in obesity rates, which actually continue to climb.

The discrepancy, discussed in the Journal of Clinical Nutrition, has experts confounded. “It’s hard to reconcile what these data show, and what is happening with the prevalence of obesity,” wrote co-author Dr. William Dietz, the former CDC director of Nutrition, Physical Activity and Obesity.¹ Doyle, Kathryn. “Despite obesity rise, U.S. calories trending downward.”  6 March 2013. Reuters. 7 March 2013. http://www.reuters.com/article/2013/03/06/us-despite-obesity-rise-idUSBRE92518620130306

The results were culled from studies conducted by the Centers for Disease Control between 1971 and 2010. Researchers surveyed several thousand people at random every few years, asking them what they ate in the previous 24 hours.  Between 1971 and 2003, they found, the average daily caloric intake rose by 314 calories. But then, starting in 2003, the trend reversed and the average person took in 74 fewer calories each day.

The drop in calories ostensibly should lead to declining obesity rates. “Seventy-four calories is a lot,” says Dr. Dietz. “We would expect to see a measurable impact on obesity.” Instead, obesity rates for women have held steady at a whopping 35 percent, and for men, they’ve risen from 27 percent to 35 percent since 1999.

The same algorithm seems to hold true for children, by the way. A separate survey of kids found that boys now take in 150 fewer calories compared to 1999, dropping seven percent from an average of 2258 calories daily to 2138 calories daily.² Sifferlin, Alexandria. “Americans Are Eating Fewer Calories, So Why Are We Still Obese?” 22 February 2013. Time. 7 March 2013. http://healthland.time.com/2013/02/22/americans-are-eating-fewer-calories-so-why-are-we-still-obese Girls now take in 80 calories fewer each day, a four percent decline. While obesity rates for girls have been holding steady, they have continued to rise for boys.

How is it possible that people are eating less and continuing to gain? Does it have to do with what they’re eating—more Big Macs, perhaps? More sugary carbohydrates? Actually, the data shows people have cleaned up their acts somewhat, eating less junk food compared to a few years ago. Another study found that fast food consumption has dropped from 12.8 percent of the average person’s diet in 2003, to the current 11.3 percent since 2007. In the children’s study, too, the facts belie the results. The data show that kids actually eat fewer carbohydrates and added sugars now compared to their skinnier days a few years back.

So again, what’s causing the counterintuitive trend toward weight gain? As Yul Bryner said in the King and I, “It’s a puzzlement!”³http://vimeo.com/45346724

Some experts say we should be patient: at the level calories have reduced to, it’s going to take a longer time to see weight reduction on a large-scale population level. Others insist that it’s already been long enough to see results.

At least some experts point to the possibility that people are getting less and less exercise.  As Jon Barron frequently points out, weight loss fundamentally comes down to burning more calories than you consume. That means that if your exercise level drops, you need to cut calories by a corresponding margin in order to maintain your weight. So one might guess that while people have taken to eating slightly less, they’ve also taken to exercising less.

Again, the facts would seem to belie the theory. According to the Bureau of Labor Statistics, Americans now exercise three times more than they did 40 years ago.⁴ “Americans Exercise More, But Not Enough.” 9 May 2012. Futurity. 7 March 2013. http://www.futurity.org/top-stories/americans-exercise-more-but-not-enough To be sure, at that increased level, the average person aged 18-60 gets only 17 minutes of exercise daily. That comes to about two hours a week, a bit short of the recommended (and still very low) two-and-a-half hours a week.

It’s hard to fathom that at 17 minutes a day, we’re exercising three times more than our parents did back in 1965. In fact, you might wonder just what the researchers count as exercise. It turns out that they mean time spent in sports, recreation, or going to the gym. The problem with such a literal interpretation is that the average person these days may go to a yoga class here and there, but that person also sits a lot more during the day than grandpa or mama did. We don’t walk as much as our parents did as a matter of routine; we don’t do as many physical chores; we spend a whole lot more time on our butts in front of screens. The bottom line is that although we may “exercise” more, we’re most likely expending a whole lot less calories than we once did.

In fact, a study just came out of the University of South Carolina linking the decline in the time women spend doing housework to the rise in obesity.⁵ O’Riordan, Michael. “Does Less Housework by Women Lead to More Obesity?” 5 March 2013. WebMD. 7 March 2013. http://women.webmd.com/news/20130304/housework-women-obesity We don’t normally think of housework as exercise, but for otherwise sedentary people, it most certainly is a calorie burner. The study found that women burn 360 fewer calories per day now compared to 1965 just on the basis of doing less cooking, cleaning, and laundry. Back then, the average woman put in 26 hours a week keeping the household running. By 2010, that figure had plummeted to 13 hours a week. Meanwhile, women doubled the time they spent watching TV.  17 minutes of formal exercise a day isn’t going to come close to making up the difference.

Study director Dr. Edward Archer says, “Our results show that we have engineered physical activity out of the workplace, out of the home, and out of our daily commute, and this has severe and dramatic consequences for our health. We need to find a way of reintegrating that activity to make up for the [decrease] in calories expended.”

The point isn’t that women should quit their jobs to stay home and cook for the brood, but the fact is, many of us are sedentary unless we go to a fitness class or the gym, and it shows on the waistline. We spend inordinate amounts of time sitting at work compared to our predecessors, and we’re so exhausted from working so many hours that it’s hard to work out. The result is that in many families, nobody is doing the cooking. Instead, food gets thrown together in a hurry, even if it isn’t junk food.

That brings us to yet one more possible reason that the decline in calories isn’t matched by a decline in obesity. The researchers mention that it’s possible that the folks they surveyed don’t accurately represent what they’ve eaten. They say that with all the news about how bad junk food and soda is, people feel ashamed to admit the truth about their diets. In fact, diet studies by the National Health and Nutrition Examination Surveys have found that men who report taking in 1500 calories per day actually consume 3000 when followed by doctors or nutritionists. Likewise, women who report an 1800 calorie intake actually consume 2400.

But an even bigger problem, as we’ve discussed in previous blogs and newsletters, is that even if people try to accurately determine the calories they’re eating, the calorie information on food labels and at restaurants may not be accurate—and we’re talking dramatically so. Indeed, studies have shown that, with the full approval of the FDA, food labels may significantly understate the amount of calories in the food being eaten—and many food companies have gone well beyond this FDA allowable fudge factor, sometimes misrepresenting calorie counts by 200% or more. In fact, people may be eating more calories and burning off fewer calories than ever before. If so, is it any wonder they’re getting heavier?