Frequent Dieting Amoung Youth May Increase Future Obesity Risk

Active Intervention Initiatives Aimed at Increasing Physical Activity in Youth Presented

Long Beach, CA – November 1, 2000 New population-based and clinical research investigating the causes and possible solutions to obesity among children and adolescents, suggests that those who were frequent dieters were significantly more likely to become overweight than those who never dieted. Additional research presented points to lessons learned from past clinical intervention studies that may help researcher better target physical activity programs for youth. The studies were presented here today at the annual meeting of the North American Association for the Study of Obesity (NAASO).

"In the last 20 years, there has been a dramatic increase in the prevalence of obesity in children and adolescents. Data from the National Heart, Lung, and Blood Institute found that 10 to 15 percent of children and adolescents, ages 6 to 17 years old, in the United States are overweight, which represents a doubling of the prevalence rates reported in earlier surveys. Research presented today looks at how to address this public health problem with a particular emphasis on eating behaviors and physical activity among adolescent girls," stated Samuel Klein, M.D., chairman of the NAASO Public Affairs Committee and professor of Medicine at Washington University School of Medicine in St. Louis, Mo.

A prospective study, conducted at Harvard Medical School and Brigham and Women's Hospital, Boston, Mass., assessed the weight change patterns of frequent dieters compared to infrequent dieters and those who never dieted. The study included 5,865 girls and 4,322 boys, ages 9 to 14 years in 1996 and followed from 1996 to 1998. Among those who were normal weight in 1996 and 1997, 27.9 percent of the girls and 6.7 percent of the boys had dieted to lose weight in the previous year. Normal weight female dieters were significantly more likely than non-dieters to report binge eating at least monthly (.5% never dieters vs. 3.1% infrequent dieters vs. 12.5% frequent dieters, p< 0.001). Between 1997 and 1998, 2.7 percent of the girls and 5.2 percent of the boys became overweight. Regardless of their intake of calories, fat or carbohydrate or their physical activity or inactivity, the frequent dieters were significantly more likely to become overweight than those who never dieted.

"Few people are able to stick to a restrictive diet for an extended period of time. Therefore, periods of dieting may be interspersed with periods of overeating," said Alison E. Field, Sc.D., assistant professor of Medicine, Harvard Medical School and Brigham and Women's Hospital, Boston, Mass., and first author of the study. "We need to encourage adolescents who are not overweight to adopt a more moderate approach to weight control. Instead of going on diets, which invariably cannot be maintained, we need to promote physical activity and eating patterns that are healthy and not overly restrictive."

Past Learnings Applied to New Programs to Increase Physical Activity A review of physical activity intervention programs was also presented today, revealing that interventions directed at promoting activity behaviors can result in increased physical activity in children while they are in physical education classes. Both school and clinically based interventions targeted to reduce sedentary behavior can decrease television watching and body fatness.

"Physical activity is a complex behavior that is determined by physiological, psychological and social factors as well as physical environment," said Russell R. Pate, associate dean for Research, School of Public Health, University of South Carolina at Columbia, S.C. "While several programs have been successful in increasing physical activity in physical education classes, it is not known whether this carries over outside of the school environment."

Researchers at the National Institutes of Health are launching a new multi-component intervention program designed to prevent the decline in physical activity levels and cardiopulmonary fitness of girls in middle school. The program is being conducted at six study centers across the U.S. from years 2000 through 2007 and will include 4,500 to 5,000 adolescent girls from diverse racial/ethnic backgrounds in 36 to 38 middle schools. Called The Trial of Activity for Adolescent Girls (TAAG), the multi-center collaborative field trial will test the effectiveness of multi-component intervention by using a school-community linked approach. The baseline data will be collected when the girls are in the sixth grade, and intervention will take place during the seventh and eighth grades. Follow-up measurement will continue into high school.

"Schools will partner with several community agencies to provide skills-building supportive environments for adolescent girls to participate in a variety of physical activity opportunities in and outside of school," said Elaine J. Stone, Ph.D., M.P.H, TAAG project administrator, National Heart, Lung, and Blood Institute, Bethesda, Md. "The findings from the research trial would provide important information on the effectiveness of strategies and programs for increasing physical activity among adolescent girls that will be helpful as we counter the trend toward inactivity, overweight, and obesity in this age group."