Too Much Food Is Responsible for Most of the U.S. Rise in Obesity Since 1970, Says Study

Sometimes complex problems have simple answers. Take the alarming rise in obesity in the United States since 1970. Researchers have speculated in the past that the cause might be a combination of factors, perhaps a lack of exercise working in concert with the spread of cheap high-calorie junk food.

Now a study led by an Australian scientist says that almost all of American weight gains over the past four decades can be attributed to a single cause: increased eating. The study, which was presented to the European Congress on Obesity, contradicts the notion that lack of physical exercise has been a major factor in the rise of obesity.

The study tracked two things: First, the number of calories adults need to maintain an ideal weight and children need to maintain normal growth; and second, the amount of calories Americans consumed on average in 1970 and into the early 2000s.
(The researchers extrapolated the amount of food Americans were eating by taking the annual amount of food produced by and imported into the United States and then subtracting the food that was exported, thrown away, or used as animal feed or for other non-human purposes.)

Based on dividing food consumption by U.S. population figures, the researchers predicted how much weight Americans would have gained over a 30-year period if food alone were the cause of the increase in obesity. They predicted that adults in the early 2000s would weigh an average of 10.8 kilograms (almost 24 pounds) more than they did in 1970.

The actual figure turned out to be an average gain of 8.6 kilograms (almost 19 pounds) over the years. While this result challenges the notion that food alone was the culprit in the long-term gain, the researchers noted that U.S. society developed an increased awareness of the need to exercise over the same span, just enough to slightly blunt the trend toward much higher weights.

In children, however, the actual weights matched perfectly with the predicted weights, indicating that food alone was the cause of weight gain.
The study’s lead researcher was Professor Boyd Swinburn, chair of population health and director of the World Health Organization Collaborating Centre for Obesity Prevention at Deakin University in Australia. Swinburn said that the best way to return to the average weights of 1970 would be for adults to drop their caloric intake by 500 calories per day and for children to drop theirs by 350.

Although stepped-up exercise could also do the trick, he said, the amount of time people would have to devote to it-two and one-half minutes daily for children and one hour and 50 minutes for adults-is unrealistic. Because the better and easier choice is reduced caloric intake, he advised that public health officials recommend eating less as the primary goal for people wanting to shed weight.

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