A higher risk of overweight or obesity is associated with screen time of more than 4 hours per day and physical activity involving less than 12,000 steps per day, according to a study published in the Journal of the American Medical Association Network Open.
Investigators included 5797 participants (mean age, 12.0 years; 50.4% boys) from the multisite Adolescent Brain Cognitive Development (ABCD) Study in the cross-sectional analysis and examined associations between body mass index (BMI) and screen time and physical activity. Study participants wore a digital device to measure daily step counts and reported their time spent using digital media during the 21-day study duration. Obesity or overweight was classified as a BMI in the 85th percentile or higher.
Overall, mean screen time and step counts were 6.5 hours and 9246.6 steps, respectively, and a total of 35% of participants had overweight or obesity, according to the report. Individuals who reported spending medium (4-8 hours) or high (>8 hours) amounts of time consuming digital media had a higher risk for overweight or obesity compared with participants with less than 4 hours of daily screen time (risk ratio [RR], 1.24; 95% CI, 1.12-1.37 and RR, 1.29; 95% CI, 1.16-1.44, respectively). Compared with high step count (>12,000 steps), medium step count (6000-12,000 steps; RR, 1.19; 95% CI, 1.06-1.35) and low step count (<6000 steps; RR, 1.30; 95% CI, 1.11-1.51) were associated with higher overweight or obesity risk.
However, study participants needed to demonstrate both high step counts and low digital consumption in order to decrease their risk for higher BMI percentile. Individuals reporting high screen time who had low step counts had a comparable risk for elevated BMI compared with individuals with high screen times and high step counts (8.26 vs 8.79 higher BMI percentile). Similarly, high and low screen time among individuals with low step counts resulted in a comparable risk for elevated BMI (8.79 vs 7.48 higher BMI percentile).
“Recreational screen time is mostly a sedentary behavior, which can lead to an increase in caloric consumption through mechanisms such as snacking in the absence of hunger and exposure to advertisements that promote unhealthy foods,” according to the study authors. “We suggest that step count and screen time categories for adolescents may be used to inform public health guidelines for adolescents.”
Study limitations include a cross-sectional nature, short study duration, and the potential for recall bias.
Nagata JM, Smith N, Alsamman S, et al. Association of physical activity and screen time with body mass index among US adolescents. JAMA Netw Open. Published online February 1, 2023. doi:10.1001/jamanetworkopen.2022.55466