Recent data suggest that since the 1970s on average we're consuming in the neighborhood of 550 additional calories daily - about a meal's worth.
The question that matters of course is, "Why"?
Undoubtedly there will be many plausible answers. The world has changed quite dramatically since the 1970s with many of the changes impacting upon the way we choose to live our lives and the foods we choose to include in them.
One thing that's certainly changed is the ubiquity of food advertisements. A CSPI report notes that even in just the decade between 1990 and 2000, a decade where we were already well into the era of Big Food, the dollars spent on food advertising increased by 50%. While I can't find the figure I'd be surprised if food advertising dollars hadn't increased at least 10 fold since 1960.
Some people believe that common sense will see them past advertisements - that they can cognitively protect themselves against their impact.
I wonder if that's true.
A study in this month's journal Obesity, albeit a small one, examined the impact that photographs of food had on 8 healthy subjects' levels of the hunger hormone ghrelin (the strongest hunger hormone identified to date). Subjects were given breakfast at 8:30am and then at 10:30am fifty pictures in 6s intervals were presented to them. In one session they were shown neutral pictures, and in the other hedonic foods. Ghrelin levels were measured throughout, and were measured every 10 minutes between 10:30am and 11:30pm. Perhaps not surprisingly, but certainly importantly, ghrelin levels were found to increase in response to the photos of hedonic foods.
What this means of course is that those hundreds of billions of dollars that are annually being spent advertising junk food - they may well be turning on the production of a powerful hormone that hundreds of millions of years of evolution has designed to make you eat. So it's not about battling your will to resist, it's about battling your body's drive to survive.
Fortunately for the species, but unfortunately for modern day nutrition, the drive to survive will likely trump our best intentions.