Sure, caloric intake is up. But we don't know whether calories per capita per day increasing is a cause, an effect, or both. Maybe all it means is that something changed to make people hungrier than they were before. For instance, there's the "fat virus". It's possible that obesity is literally contagious and more people caught it with, say, the growth of air travel.
http://www.webmd.com/diet/news/20070820/obesity-virus-more-b...