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Planet Health Program Reduces Obesity in Middle-School Girls
A school-based program that teaches better dietary habits and
reduces television viewing was found to be effective in reducing the
prevalence of obesity in middle-school girls, but not boys, according to
an article in the April issue of Archives of Pediatrics and Adolescent
Medicine.
Lead author Steven Gortmaker, senior lecturer in the Department of Health and Social Behavior, described Planet Health as "an interdisciplinary program that fits within existing math, science, language arts, social studies, and physical education classes in the sixth, seventh, and eighth grades. The goals of the program are to decrease the amount of time kids spend watching television, to increase physical activity, and to promote consumption of fruits and vegetables."
The results of the study, "Reducing Obesity via a School-Based
Interdisciplinary Intervention Among Youth," are based upon a
comparison of five control schools and five schools that received the
Planet Health intervention for two years. The schools were in four
Massachusetts cities, and 1,295 students participated in the research.
Obesity was defined as a composite indicator based on a body mass index (BMI) and a triceps skinfold. BMI is a standard measure for obesity that is a calculation of a person's weight in kilograms divided by his or her height in meters squared. BMIs, however, can be influenced by frame size and do not differentiate between lean-body mass and fatness. To better identify obesity, the researchers included the triceps skinfold measure, which is a measure of the fatty tissue just beneath the skin.
According to Gortmaker, "Over the last 30 years, the prevalence of obesity among children and youth has been increasing rapidly, to the point where we now find about 25 percent of boys and girls are obese. Because obesity is a major cause of diabetes, heart disease, and other chronic health conditions, this is a serious problem. Obesity is the primary nutritional problem among young people."
Planet Health was successful in reducing obesity among girls, from 23.6 percent to 20.3 percent, while the prevalence of obesity increased 2.2 percent in the control schools not receiving the Planet Health intervention. "Perhaps most impressively," said Gortmaker, "we found that girls who were already obese at the beginning of the study more than doubled their chances of becoming non-obese by the end of the study."
While the intervention consisted of the three elements of improving diet, increasing physical activity, and decreasing television viewing, it is the link between time spent watching television and obesity that was most clearly explicated by this study. "We found that changes in television-viewing time were directly related to changes in obesity," said Gortmaker. "For each hour of reduction in television-viewing time per day we found about a 15 percent reduction in risk of obesity."
Steven Gortmaker, senior lecturer in the Department of Health and Social Behavior, is the primary investigator behind the Planet Health intervention.
"The mechanism is simple," explained Gortmaker. "At the
beginning of the study we ascertained that the children were watching
about three hours of television each day. That translates into 21 hours a
week of sedentary time in which the kids aren't burning many calories. In
addition, they're exposed to numerous commercials that are designed to
reinforce the consumption of primarily high-calorie foods. This
creates an imbalancea lot of inactivity coupled with extra
consumption. Muliply by 365 days per year, and the result, too often, is obesity."
Planet Health worked to reduce time spent watching television through a variety of means. "A component taught in math classes was to have the students estimate the total number of hours that they've spent watching TV in their lifetimes. Usually, the students are surprised by the large numbers and begin to realize that they're spending a substantial fraction of their lives in front of the television," said Gortmaker.
"The students are also encouraged, in their physical education classes, to set goals for replacing some of their time spent watching television with physical activities such as sports or walking," continued Gortmaker. "In addition, the program includes a 'television power-down,' which is a week in which the students work with their families to identify alternate activities to watching television."
The researchers aren't certain why the program was effective for girls, but not for boys. Gortmaker speculated, "Among youth these ages, there are developmental differences between girls and boys that may account for the results. It may also be that boys at these ages are less attuned to issues of diet and activity compared to girls."
Having shown the program to be successful, the researchers
are working to increase the number of schools that utilize the
program, and are holding discussions with representatives of the Boston
public school system. They are also working with a book publisher to
make the curriculum available, this fall, nationwide.
See also AMA video coverage
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