Do sugar-sweetened beverages cause weight gain? That’s been the million-dollar question, with numerous studies over the years consistently having, well, inconsistent results. Now, a new study—actually a review of 17 review studies—has revealed a disconcerting, but not-so-surprising, finding: The answer depends on who is funding the research.
According to the study, published online in PLOS Medicine, 61 percent of the reviews found an association overall between sugary beverages and weight gain or obesity. But when the researchers sorted the reviews by whether they had any ties to food companies (like Coca-Cola and Pepsi), they found that the industry-affiliated ones were five times more likely to not find a link between beverage consumption and body weight, compared to those with no industry ties.
For example, one industry-sponsored review concluded that sugary beverages lead to “no overall change in body weight.” Another concluded that the link between sugary drinks and obesity is “only judged as possible.” Overall, about 80 percent of industry-affiliated reviews found insufficient evidence of an association.
In striking contrast, about 80 percent of the reviews done by independent researchers linked sugary drinks to increased body weight, coming to such conclusions as “A high intake of calorically sweetened beverages can be regarded as a determinant of obesity.”
As the new paper states, “The use of industry funding for scientific research might influence the results of published studies, leading to conclusions that could ultimately support the industry’s interests.” It further says that the authors of systematic reviews “may draw their conclusions in ways consistent with their sponsors’ interests.” This holds true, of course, not just in the food and beverage industries, but in any industry where high profits are at stake.
Going forward: The solution to such conflicts of interest is not necessarily to stop industry-sponsored research—after all, in many cases, who else would fund the studies? But it’s essential that strict guidelines be established (and enforced) to eliminate biases—for instance, by not allowing the sponsoring company to be a part of the study’s selection process or interpretation of results, and by making all data available to other researchers. As for sugary drinks, we think this new review—along with hundreds of studies linking sweetened drinks to diabetes, heart disease and premature mortality—provides even more reason to avoid or limit their consumption.