According to Binkley, the study confirms that the problem of obesity is a confoundingly complex one. At most, the study suggests that the types of food one eats may not matter as much as the amount of calories consumed or the amount of exercise. "Fast-food restaurants may be to blame in some way for the nation's weight problems, but in general there is little evidence of that," he says.
Taking the study one step further, Binkley then compared the CDC data with the 1990 Sales Area Marketing Inc. (SAMI) data on warehouse grocery sales. Again, he found little correlation between types of food consumption and obesity.
"Actually, I couldn't find much of a relationship at all between long-term dietary changes and increasing obesity," Binkley says.
The data from the grocery wholesalers showed that populations that consume convenience foods and trendy foods such as jarred peppers or black olives are less likely to be obese than groups that consume more traditional foods such as canned goods, frankfurters or pudding.
Randy Gretebeck, a registered dietitian and exercise physiologist in Purdue's Department of Foods and Nutrition, says it's not uncommon for large studies to provide results that confound nutritionists. "Large studies have found that food intake doesn't seem to be a good indicator of obesity, but we know it should be. Also, recent studies have found that fat consumption has gone down across the nation, yet obesity continues to increase," he says. "Right now, more and more people are pointing to decreasing physical activity as a reasonable explanation."
Besides reduced activity and exercise, Gretebeck says, there may be other possible explanations for the seeming anomaly, "and what we really need to do is to investigate further."