Research Agrees: Get Over Calories

I've remarked before on the absolutely bizarre relationship that Americans (in particular) have with the most fundamental unit of nutrition: the calorie. The calorie is merely a measurement of the energy supplied by foods and drinks; the energy that we use to continue living, and without which we would basically self-destruct, physiologically speaking. Yet we hold calories in the same regard as other food fad scares, like gluten or "carbs" or worse. That's weird and reflective of some real confusion regarding our basic relationship with food.

I get that as first-world humans we have a super-abundance of calorie-rich foods and so good reason to closely monitor our consumption of said foods and their relative caloric content. But that's turned into something of a cultural obsession, when really we could make reasonable eating decisions without spreadsheets, just through a few basic principles and maybe even good old intuition.

A study out this week from a team based at Stanford University offers more of a quantitative defense of calories. Researchers crunching data from the massive National Health and Nutrition Examination Survey (NHANES) have found that American obesity (as in the epidemic) might not have much to do with calories at all. In fact, over the past 20 years, calorie consumption mainly stayed flat, while daily physical activity went through the floor. We're gaining weight because we don't move as much as we used to, according to the investigators.

Specifically, the percentage of women reporting no daily physical activity jumped from 19.1 percent in 1994 to 51.7 percent in 2010, while the same for men jumped from 11.4 percent to 43.7 percent during the same period. The average body mass index spiked for both groups.

"These changes have occurred in the context of substantial increases in the proportion of adults reporting no leisure-time physical activity, but in the absence of any significant population-level changes in average daily caloric intake," said lead author Uri Ladabaum in a statement. "At the population level, we found a significant association between the level of leisure-time physical activity, but not daily caloric intake, and the increases in both BMI and waist circumference."

The study is paywalled, but most of what you need is in the chart below, and you're free to comb the open-access NHANES datasets at your leisure.

This is not the last word, of course. One CDC study published in 2004 examined calorie consumption trends over the 30 years prior and found definite, significant spikes in daily intake. "The study, conducted by the Centers for Disease Control and Prevention and reported in the current edition of its Morbidity and Mortality Weekly Report, found that in 1971 women ate 1,542 calories on average, compared with today's 1,877, while men went from 2,450 calories a day to 2,618," The New York Times reported.

The primary reason cited then was an increase in calorie-rich carbohydrate consumption as a share of all food eaten; consumers were having low-fat diets pushed from every angle for a good long while during the CDC study window, while carbs were touted as a weight-loss panacea. The calorie terror of recent years might have washed away some of the increases seen in that CDC study over recent years, but it surely can't account for all of the discrepancy. I've asked Uri Ladabaum about this and will update if I hear back.

In any case, there's an underlying point here about how we get our ideas about nutrition, and why those ideas are so fucked up. These finds are surprising because everyone, from the paleo dieter to their suburban mom, has had the evilness of calories drilled into their skulls relentlessly. It's much, much easier to sell "low calorie" than it is to sell "high activity."