A study released at the European Congress on Obesity in Amsterdam has found that an increase in food intake, not a decrease in activity, is to blame for the obesity epidemic.

Professor Boyd Swinburn (Chair of Population Health at Deakin University in Australia) led the study.

The study followed a three-step process:

1. Finding How Many Calories We Need

Swinburn and colleagues began by quantifying how much food adults need to maintain their weight and how much children need to grow normally. (This part of the study involved 1,399 adults and 963 children.)

2. Working Out Theoretical Results Of The Increased Food Intake

The researchers used national food supply data from the 1970s and the early 2000s to predict how much weight Americans would have gained over that period, if increased food intake was the only factor.

3. Comparing Theoretical And Actual Results

The actual weight gained was determining from a survey that recorded the weight of Americans during the same periods (1970s and early 2000s).

Comparing the theoretical and actual figures demonstrated that children's weights had increased by exactly what would be expected from the increased food intake alone. Adults had put on slightly less weight than the extra food would have indicated (8.6 kilos heavier instead of 10.8).

Swinburn suggested that this might mean physical activity had actually increased slightly in adults.

This may also suggest that we're all scoffing down mountains of junk food, but the actual extra food intake is a fairly modest amount per day - it just adds up over time. In a statement, Swinburn said:

To return to the average weights of the 1970s, we would need to reverse the increased food intake of about 350 calories a day for children (about one can of fizzy drink and a small portion of French fries) and 500 calories a day for adults (about one large hamburger).

One reason why we're all eating more today than in the 1970s could be due to larger portion sizes: many of us tend to clear what's on our plate, whether or not we're still hungry.

Do the results of this study match your experience? Are you (or family members) eating more than you were in the past? What can we do to reverse the trend?