Three studies published over the weekend in the New England Journal of Medicine (NEJM) provide compelling new evidence linking sugar-sweetened sodas and other beverages to obesity.
The studies, two of which were clinical trials involving children and teens, add support to recent efforts to reduce Americans’ consumption of sugary beverages, including New York City’s recently adopted ban on the sale of large sizes of such drinks.
Americans drink an astounding amount of sugary beverages, such as sodas, fruit-flavored drinks, sports drinks, energy drinks and highly sweetened coffees and teas. According to the Centers for Disease Control and Prevention, half of Americans drink a sugar-sweetened beverage on any given day, and 25 percent down more than 12 ounces of them daily.
One of the new NEJM studies, led by researchers at VU University in the Netherlands, involved 641 mostly normal-weight schoolchildren, aged 4 through 11 years, who reported drinking sugar-sweetened beverages regularly. Half of the children were randomly assigned to receive a non-carbonated sugar-sweetened beverage with their school lunch. The other half received an artificially sweetened beverage.
After 18 months, the children drinking the sugary beverages had gained, on average, significantly more weight than those drinking the artificially sweetened ones: 16 pounds 3 ounces versus 14 pounds 1 ounce.
The study has its limitations. Most notably, about a quarter of the students dropped out of the study before it ended (although while they were in the study, their weight paralleled that of those who saw the study through). In addition, all the students were healthy and white. The researchers say it’s unclear if the study’s results would be similar in other ethnic groups, in obese children, or in adults.
The researchers conclude their study by pointing out that U.S. children take in, on average, almost three times as many calories from sugar-sweetened beverages as the amount provided to the Dutch children in the clinical trial.
“We speculate that decreased consumption of such beverages might reduce the high prevalence of overweight in [U.S.] children,” they write.
A second study, led by researchers at Boston Children’s Hospital, involved 224 overweight and obese ninth- and tenth-graders (the mean age was 15). At the start of the study, all the teens said they drank at least 12 ounces of sugary beverages daily. The researchers divided the students into an experimental and a control group. The experimental group received a one-year intervention program designed to get them to drink less sugar-sweetened drinks. The program included home deliveries of bottled water and non-sugary drinks (most sugar-sweetened beverages are consumed in the home), monthly 30-minute motivational telephone calls with the parents, and three 20-minute check-in visits with the teens.
The control group received two $50 supermarket gift cards to encourage them to stay in the study, but they received no instruction on what to buy with the card.
At the end of the year, the teens in the intervention group had gained, on average, only half as much as those in the control group: 1 pound 7 ounces versus 3 pounds 5 ounces.
Although the intervention part of the study ended after one year, all the teens were followed for another year. At that point, no difference in weight gain was observed between the two groups. The authors do not know why the differences disappeared, although one possible explanation is that the teens in the experimental group returned to their old beverage habits.
The major limitation of this study was the small number of students involved.
For a third study, Harvard University researchers used genetic and dietary data from 33,000 adults who were participating in three ongoing long-term health studies. Each participant was given a genetic-predisposition-to-obesity score based on how many of the 32 gene variants associated with obesity he or she had. (Although each of us has some genetic risk of becoming obese, research suggests that the more of these 32 gene variants we have, the greater our individual risk.)
Using self-reported dietary information, the researchers then divided the participants into four groups based on how much sugar-sweetened beverages they consumed: less than one serving per month, one to four servings per month, two to six servings per week, and one or more servings per day.
After crunching the resulting data, the researchers found that the risk of becoming obese among the participants with the highest number of obesity-related gene variants was more than twice as great in those who drank the most sugary beverages compared to those who drank the least.
“Taken together, these three studies suggest that calories from sugar-sweetened beverages do matter,” writes Yale University pediatric endocrinologist and obesity expert Dr. Sonia Caprio in an NEJM editorial that accompanies the three studies. “Furthermore, policy decisions about sugar-sweetened beverages should not be considered in isolation. Other strategies to achieve and maintain normal weight, including increasing physical activity, will be important to stem the obesity epidemic and its effects. The time has come to take action and strongly support and implement the recommendations from the Institute of Medicine, the American Heart Association, the Obesity Society, and many other organizations to reduce consumption of sugar-sweetened beverages in both children and adults.”
You can read all three studies and the editorial at the NEJM website.