Soft drinks, sports drinks and other sweetened beverages are now known to contribute to Americans’ obesity problem. This link has led some policy makers to address the problem by restricting access or serving sizes, including the New York City health board’s effort to ban restaurants, delis, movie theaters, food carts and stadiums from selling sugar-sweetened drinks in cups larger than 16 ounces.
Now, less than a week after an appeals court ruled against the proposed ban, a study in Pediatrics has found evidence that the sugary drink–obesity link occurs in the youngest population to be studied along this dimension—toddlers and preschoolers. Following 9,600 children from birth through age five, the researchers identified sugary drink patterns in children as young as two that set the stage for greater weight gain a few years later. The sugary drinks studied include sodas, sports drinks and any other sugar-added beverages or juice drinks that were not 100 percent juice.
The study’s size and lengthy follow-up period make its findings particularly valuable to physicians such as Dyan Hes, medical director of Gramercy Pediatrics in Manhattan, who has been lobbying for public policies like soda taxes that would make these drinks less attractive to families. “It’s a fantastic study because we need more evidence,” Hes says. “We know that sugar-sweetened beverages are the greatest contributor to increased obesity in young children because they’re cheap. It shows that by giving your children sugar-sweetened beverages by age two, you’ve already set up habits that are very hard to break.”
The study did not find that two-year-olds who drank at least one sugar-sweetened beverage a day were heavier than their nondrinking peers right away, but toddlers who drank sugary drinks daily were heavier by age five. In fact, they were 1.43 times more likely to be obese than preschoolers who consumed sugary drinks less than daily, even after accounting for other factors that could influence weight gain. Mark DeBoer, assistant professor of pediatrics at the University of Virginia, says the findings support the hypothesis that regular consumption of sugar-sweetened beverages has a cumulative effect over time. “We were struck by these data that even at a very young age, the sugar-sweetened beverages contribute to weight gain,” DeBoer says, “and we wanted to put this information out for pediatricians and for families to help them make healthier choices for their children.”
Sugary drinks versus unhealthy lifestyles
Interviews also revealed a pattern that has shown up in other studies—that drinking sugar-sweetened beverages correlates with additional factors already linked to obesity: Among the children who drank at least one sugary drink serving daily, a higher proportion had overweight or obese mothers and a higher proportion watched at least two hours of television daily, compared with less frequent drinkers. More of the sugary drink consumers were also black, Hispanic or in low-income families. These factors have all been shown to play a part in unhealthy weight gain among kids. Adjustments for these variables in this study, however, failed to eliminate the link between sugary beverages and obesity by age five.
Still, Yoni Freedhoff, an obesity specialist and assistant professor of family medicine at the University of Ottawa, says that observational studies like this one should control as well for how frequently families eat out, how frequently they eat together, the timing of meals and snacks, the types of meals they eat, whether they skip breakfast, and how much juice or chocolate milk they drink. “Maybe sugar-sweetened beverages are a marker behavior for other dietary problems and concerns,” Freedhoff says, although he agrees that sugar-sweetened beverages contribute to unhealthy weight gain. DeBoer’s team has some of that additional data, but it is difficult to statistically address many confounding factors in a population of nearly 10,000 children.
In contrast, Walter Willett, a nutritional epidemiologist at Harvard School of Public Health, agrees that strong controls for lifestyle factors are important, but vouched for the analysis in this study. “Socioeconomic status, parents’ BMI [body mass index] and television watching are strong correlates of other lifestyle factors that are potential confounders,” Willett says, “so they have at least partly controlled for other variables indirectly.” Also, some of the previous findings that strongly link sugar-sweetened beverages and obesity in older children and adults include randomized trials. So, given the similar underlying biology for weight gain across age groups, the DeBoer findings are likely valid, he says.
More calories, less filling
There is a general consensus on why sugar-sweetened beverages are so instrumental in weight gain. Beverage calories are not typically filling. “If you drink 110 calories with your meal, you are not going to eat 110 calories less from the food,” Freedhoff says. “We should be reducing liquid-calorie consumption from all sources, regardless of our ages. I’m not aware of any beverage whose health benefits aren’t obtainable from far more satiating solids.”
In fact, several past studies have found that children who regularly drink-sugar sweetened beverages have about a 17 to 20 percent increase in their overall daily caloric intake. Although an editorial accompanying the DeBoer study suggested milk as an alternative beverage—it may provide more satiation and perhaps displace some food calories—studies by both DeBoer and Willett have found that skim and 1 percent milk are also linked to unhealthy weight gain in kids. The jury is still out on whole milk. “I would love to see some studies looking at liquid calories as a whole rather than trying to suss out or demonize one particular beverage,” Freedhoff says.
Yet Freedhoff is disappointed that the New York City law failed because it might have helped make consumers more conscious of their choices. The failure, according to Hes, was most likely due to logistical problems with its execution. “On a large scale, it was just a very cumbersome rule to implement,” she says. “What I think is much better is to do a tax, like you do with cigarettes. If you tax sugar-sweetened drinks, people will buy less of them. They’re too affordable.”
Regardless of how it is done, Freedhoff says drinks with added calories might be a good starting point. “Given the ease with which liquid calories can be cleaved from our diet,” he says, “they are a very real and obvious first target if we’re talking about obesity and weight.”