Study Links Soft Drink Consumption to Childhood Obesity

A child’s odds of becoming obese increase by 60 percent with each additional daily serving of sugar-sweetened drinks. This was the conclusion of a recent study from the Department of Medicine at Children’s Hospital in Boston and the Harvard School of Public Health. The results of the study, led by David S. Ludwig, M.D., Ph.D., director of the obesity program at Children’s Hospital, suggested that the link between soft drink consumption and obesity is independent of food intake, television viewing, and physical activity.

Most adolescents, 65 percent of girls and 74 percent of boys, consume soft drinks daily and most of these soft drinks are sugar-sweetened rather than artificially sweetened. In 1994-95, adolescent boys were consuming nearly 20 ounces per day. “The average teenager is getting 15 to 20 teaspoons a day of added sugar from soft drinks alone,” said Dr. Ludwig. “Consumption rates among children have doubled in the last decade.” The researchers hypothesized that this could be one factor contributing to the 100 percent increase in the prevalence of childhood obesity in the U.S. between 1980 and 1994.

This prospective study followed 548 children ages 11 to 12 in the Boston area from October 1995 to May 1997. It examined the relationship between sugar-sweetened drink consumption, BMI, and incidence of obesity. Investigators obtained BMI, skinfold thickness, dietary intake, physical activity, and television viewing data at study outset and again 19 months later. The Youth Food Frequency Questionnaire (YFFQ) measured average drink intake—including sugar-sweetened drinks—as well as dietary fat and total energy intake. Sugar-sweetened drinks were defined as soda, Hawaiian Punch, Kool-Aid, lemonade, sweetened ice tea, and other sugared fruit drinks.

Fifty-seven percent of the children increased their daily sugar-sweetened drink consumption over the 19-month period, with a quarter drinking more than one extra can of soda or glass of sugared beverage per day. After making adjustments for other factors that might affect body weight, including diet, physical activity levels, time spent watching television, and total energy intake, the researchers found that BMI increased with each additional serving. Thirty-seven children who were not considered obese at baseline were obese by the end of the study.

A reverse trend was noted among children who increased their consumption of diet soft drinks, with the incidence of obesity declining in this group. Thirty-five children obese at baseline were no longer obese at follow-up.

There is some controversy about the relationship of sugar-sweetened drinks to childhood obesity. The study authors acknowledge the limitations of their research, including their inability to fully control for changes in body composition over time resulting from normal growth and development. Nevertheless, they conclude that “sugar-sweetened drink consumption could be an important contributory factor” in the growing rates of pediatric overweight.

“These data suggest that people aren’t compensating” for excess energy intake in liquid form by eating less at meals, said Dr. Ludwig. According to France Bellisle, Ph.D., of the Institute of Health and Medical Research in France, very young children (4 to 5 years old) adjust their food intake to offset extra calories consumed as liquid, but lose this ability as they grow older. Obese children are even less accurate than other children at compensating for prior energy intake. The study’s authors conclude that this physiological mechanism is a viable explanation for their findings that sugar-sweetened drinks contribute to childhood obesity.

This study, supported in part by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), was published in the February 17, 2001 issue of The Lancet. Subscribers can access the article at www.thelancet.com. s