Food, Inc.

A Robert Kenner Film
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Eating Made Simple

Sodas and obesity

Sodas and Obesity

Food, Inc.: soft drinks

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Sugars and corn sweeteners account for a large fraction of the calories in many supermarket foods, and virtually all the calories in drinks -- soft, sports and juice -- come from added sugars.

In a trend that correlates closely with rising rates of obesity, daily per capita consumption of sweetened beverages has grown by about 200 calories since the early 1980s. Although common sense suggests that this increase might have something to do with weight gain, beverage makers argue that studies cannot prove that sugary drinks alone -- independent of calories or other foods in the diet -- boost the risk of obesity. The evidence, they say correctly, is circumstantial. But pediatricians often see obese children in their practices who consume more than 1,000 calories a day from sweetened drinks alone, and several studies indicate that children who habitually consume sugary beverages take in more calories and weigh more than those who do not.

Nevertheless, the effects of sweetened drinks on obesity continue to be subject to interpretation. In 2006, for example, a systematic review funded by independent sources found sweetened drinks to promote obesity in both children and adults. But a review that same year sponsored in part by a beverage trade association concluded that soft drinks have no special role in obesity. The industry-funded researchers criticized existing studies as being short-term and inconclusive, and pointed to studies finding that people lose weight when they substitute sweetened drinks for their usual meals.

These differences imply the need to scrutinize food industry sponsorship of research itself. Although many researchers are offended by suggestions that funding support might affect the way they design or interpret studies, systematic analyses say otherwise. In 2007 investigators classified studies of the effects of sweetened and other beverages on health according to who had sponsored them. Industry-supported studies were more likely to yield results favorable to the sponsor than those funded by independent sources. Even though scientists may not be able to prove that sweetened drinks cause obesity, it makes sense for anyone interested in losing weight to consume less of them.

The examples I have discussed illustrate why nutrition science seems so controversial. Without improved methods to ensure compliance with dietary regimens, research debates are likely to rage unabated. Opposing points of view and the focus of studies and food advertising on single nutrients rather than on dietary patterns continue to fuel these disputes. While we wait for investigators to ?nd better ways to study nutrition and health, my approach -- eat less, move more, eat a largely plant-based diet, and avoid eating too much junk food -- makes sense and leaves you plenty of opportunity to enjoy your dinner.

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Marion Nestle is Paulette Goddard Professor in the department of nutrition, food studies and public health and professor of sociology at New York University. She received a Ph.D. in molecular biology and an M.P.H. in public health nutrition from the University of California, Berkeley. Nestle's research focuses on scientific and social factors that influence food choices and recommendations. She is author of Food Politics (2002, revised 2007), Safe Food (2003) and What to Eat (2006). She also writes a popular nutrition blog, Food Politics.

Reprinted with permission. Copyright © 2007 by Scientific American, a division of Nature America, Inc. All rights reserved. For more information about the issue, go to: