Longitudinal Examination of the Incidence of Obesity in Adolescent Females

The persistence and incidence of obesity was investigated in 61 black and 29 white females residing in Knox County, Tennessee. These girls were 16.0 ± 0.5 years of age and had been previously studied at 9, 10, 11, and 14 years of age. Data collected on these girls and 40 additional 12- and 14-year-old girls included height, weight, triceps circumference, triceps skinfold thickness, 24-hour dietary recalls, and an activity recall. A questionnaire concerned with attitudes toward physical activity was devised, pilot tested, and administered. An obesity index was devised from height, weight, and triceps measurements of the girls with the use of factor analysis. Girls were divided into quartiles according to the obesity index and into three groups according to the triceps skinfold measurements. A girl was considered obese if she was in the 4th obesity index quartile or had a triceps skinfold measurement equal to or greater than the 85th percentile as determined from the Ten State Nutrition Survey data.

The persistence of obesity decreased as the time between examinations increased, although a significant relationship still existed between age 9 and age 16. Seventy-one percent of the girls who were obese when 9 years old still were obese at age 16 according to the obesity index method; 87% of the thin or normal girls remained so over the 7-year period. Forty percent of the girls remained obese according to the triceps skinfold method and 85% remained thin or normal over the 7-year period.

Incidence of obesity ranged from 17% when the girls were 10 years of age to 27% for the 11-year-olds. At age 16, 19% of the sample were obese.

The obese girls consumed significantly fewer kilocalories than the thin girls. There were no significant differences for activity levels or attitudes toward physical activity among the thin, normal, and obese girls. These results indicate that factors other than excessive energy intake or low energy expenditure may be responsible for the obese state of some individuals.