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Is junk food making us fat? Why cutting candy, soda may not be enough

It's easy to blame junk food, fast food and sodas for weight problems, but they may not be a driving force in America's obesity crisis.
/ Source: TODAY

It’s easy to blame junk food, fast food and sodas for our weight problems. Sugary sodas — with their more than 220 calories per serving — have been called public enemy No. 1 in the fight against obesity.

What if junk food or soda actually plays only a limited role in America’s fat crisis?

In a new study, Cornell researchers were surprised to find people who are overweight and people with “healthy” BMIs eat junk food about the same number of times each week. The paper, published Thursday in Obesity Science & Practice, provides more evidence that the causes of obesity and weight are more complicated than the cliché of couch potatoes scarfing down fast food and guzzling soda every day.

“Junk foods like soda, potato chips, candy, fast foods, those are foods that can make us fat if we eat them to excess … [But] they don’t appear to be the driving factor if you look at obesity in the United States,” says David Just, co-director of the Cornell Food and Brand Lab.

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Just and his colleague Brian Wansink — co-director of the Cornell Food and Brand Lab — looked at data from the National Household and Nutrition Examination Survey (NHanes). About 5,000 people participated in food recalls, where they reported what they ate over the past 24 hours, and in-home surveys, where researchers calculated BMI using height and weight measurements. Specifically, Wansink and Just examined subjects’ BMI and how often people ate fast food, junk food and candy.

People with BMIs from 18.5 to 40, which spans from normal weight to obese, enjoyed these foods about the same number of times per week, meaning there was no statistically significant difference. In fact, for 95 percent of the population, enjoying soda, candy, and fast food is not associated with BMI.

“Seeing how flat this line was for all these foods was a bit shocking to me," says Just.

The study examined frequency, but did not look at portion size or exercise habits. So it's possible — maybe even likely — that healthy weight people eat less bad food at a sitting than overweight people. The Cornell researchers next plan to look at whether serving sizes of candy, junk food, and fast food are associated with increasing BMI.

The Cornell study should not be seen as permission to overindulge, says Just. Instead, it tells us again that demonizing one type of food or beverage can backfire.

“To me, the most important takeaway is not to focus narrowly on bad foods. It is more complicated than that,” he says. “It is a wider part of our diets … we just really need to cut back overall.”

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Take soda bans. Restricting access to huge servings of sodas may encourage some healthier behaviors, but others may wrongly believe drinking less soda will automatically improve health.

Sure, they might lose a few pounds but if they don't look at overall diet and exercise, their weight problem won't be solved.

“We can’t have our whole obesity fight policy be ‘let’s make sodas difficult to get.’ It is not enough and not productive,” says Just.

Not just calories

Kristin Kirkpatrick, manager of wellness nutrition services at Cleveland Clinic’s Wellness Institute, who was not involved with the study, agrees public health messages shouldn’t be narrowly focused.

“We have to shift our thinking from looking simply at calories,” she says. “I think the most important thing is [looking at] the overall diet.”

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Wendy Hahn, a clinical nutritionist at University of Wisconsin Health, who also wasn’t involved in the study, also agrees.

“The bottom line is to enjoy your food and eat less of it,” she says.