It looks as if the obesity crisis in America isn’t going away anytime soon. In its annual state-by-state survey, the Robert Wood Johnson Foundation recently reported that the incidence of obesity among adults has doubled, or nearly so, in 17 of the 50 states over the last 15 years. What’s even more staggering is that 20 years ago, not one state reported an obesity rate higher than 15%. Now, obesity incidence tops 15% of the population in all 50 states.
Yes, we’re not as active as we should be, and we eating more than ever. But why has our calorie intake gone up so much in recent years? High calorie foods, bigger portions and more frequent eating contribute, to be sure. But a recent study1 attempted to tease out which of these factors have contributed most to America’s problem with girth control.
The study, conducted by researchers at the University of North Carolina, looked at changes in American eating habits by examining data from nationwide surveys over four time periods, with the first beginning in 1977 and the last survey concluding in 2006. Over this 30 year period, our total calorie intake increased a whopping 570 calories per day, with nearly half that increase occurring in just the last ten years alone.
But it wasn’t just the total number of calories we’re eating that was of interest. The researchers really wanted to understand how these excess calories were making their way to our plates. So, they examined the data more carefully to look at how each of three factors (meal frequency, portion size, and calorie density—the number of calories ‘per bite’ in the foods we eat) have affected the overall uptick in our calorie intake.
It turns out that increased snacking takes much of the blame. In the past 30 years, the average number of ‘eating occasions’ for US adults has gone from 3.8 times per day to just about 5. And we shortened the time interval between eating occasions by a full hour. We now eat an average of every 2 ½ hours, compared to the 3 ½ hours we used to wait between feedings in the 1970s.
Here’s how the numbers broke down: Between 1977 and 2006, our daily calorie intake from meals (counting both foods and beverages) went up by about 125 calories. If you single out beverages alone, we’re slurping down about 135 calories more per day than we did in 1977—largely because our portion sizes have gone up.
That pales in comparison to what increased snacking has contributed. During the same time period, snacking piled on an additional 300 calories a day. The calorie density of the foods we’re eating didn’t really change that much. In other words, our foods didn’t get ‘more fattening’—we’re just eating more food and eating it more often.
This isn’t to say that eating five times a day is a bad thing. If you don’t exceed your daily calorie needs, it doesn’t matter if you eat two times a day or twelve. But the more often you eat, the less you need to eat each time. And that’s an adjustment that many Americans don’t seem to be making. The calories are piling up because we just keep eating more, and more often.
1 Popkin and Duffey. PLoS Medicine. June 2011, 8:6, 1-7.