I am always indebted to Joel Moskowitz of the University of California School of Public Health’s Center for Family and Community Health for his almost daily forwarding of research on obesity. His recent postings include data from the Centers for Disease Control (CDC). The CDC has just released preliminary results of the 2008 National Health Interview Survey. These include, among other measures, data charts and tables on obesity (rates still rising steadily since 1997), physical activity (no measurable change), and diabetes (rising in parallel with obesity).
Interpretation: if physical activity rates have not changed, then the reason obesity rates are going up is because people are eating more calories.
Plenty of evidence backs up this idea. All you need to do to see why people are eating more is to take a look at Time magazine’s discussion of the implications of calorie labeling: “Would you like 1,000 calories with that?”