OBJECTIVE

Many adolescents do not meet national guidelines for participation in regular moderate or vigorous physical activity (PA); limitations on sedentary behaviors; or dietary intake of fruits and vegetables, fiber, or total dietary fat. This study evaluated a health care-based intervention to improve these behaviors.

DESIGN

Randomized controlled trial.

SETTING

Primary care with follow-up at home.

PARTICIPANTS

Eight hundred seventy-eight adolescent girls and boys aged 11 to 15 years.

INTERVENTIONS

Two experimental conditions: (1) Primary care, office-based, computer-assisted diet and PA assessment and stage-based goal setting followed by brief health care provider counseling and 12 months of monthly mail and telephone counseling and (2) a comparison condition addressing sun exposure protection.

MAIN OUTCOME MEASURES

Minutes per week of moderate plus vigorous PA measured by self-report and accelerometer; self-report of days per week of PA and sedentary behaviors; and percentage of energy from fat and servings per day of fruits and vegetables measured by three 24-hour diet recalls. Body mass index (calculated as weight in kilograms divided by the square of height in meters) was a secondary outcome.

RESULTS

Compared with adolescents in the sun protection condition, girls and boys in the diet and PA intervention significantly reduced sedentary behaviors (intervention vs control change, 4.3 to 3.4 h/d vs 4.2 to 4.4 h/d for girls, respectively [P = .001]; 4.2 to 3.2 h/d vs 4.2 to 4.3 h/d for boys, respectively [P = .001]). Boys reported more active days per week (intervention vs control change: 4.1 to 4.4 d/wk vs 3.8 to 3.8 d/w, respectively [P = .01]), and the number of servings of fruits and vegetables for girls approached significance (intervention vs control change, 3.5 to 4.2 servings/d vs 3.5 to 3.9 servings/d, respectively [P = .07]). No intervention effects were seen with percentage of calories from fat or minutes of PA per week. Percentage of adolescents meeting recommended health guidelines was significantly improved for girls for consumption of saturated fat (intervention vs control change, 23.4% to 41.0% vs 18.5% to 31%, respectively [relative risk, 1.33; 95% confidence interval, 1.01-1.68]) and for boys' participation in d/wk of PA (intervention vs control change, 45.3% to 55.4% vs 41.9% to 38.0%, respectively [relative risk, 1.47; 95% confidence interval, 1.19-1.75]). No between-group differences were seen in body mass index.

CONCLUSIONS

Improvements in some diet, PA, and sedentary behaviors in adolescents can be enabled through the use of a 1-year, integrated intervention using the computer, health provider counseling, mail, and telephone. The amount of intervention received may contribute to its efficacy.