Adolescents who replace 30 minutes of sedentary time each day with moderate-to-vigorous physical activity may reduce their insulin resistance by nearly 15%, according to preliminary research presented at the American Heart Association's EPI|Lifestyle Scientific Sessions 2026. The study analyzed health data from Project Viva, a long-term study of women and children in Eastern Massachusetts, and found that substituting sedentary time with sleep also reduced insulin resistance by nearly 5%, though shifting to light physical activity showed no significant effect.
The research examined 802 participants with an average age of nearly 13 years who wore accelerometers and kept sleep logs for 7-10 days to track their daily activities. The data revealed that adolescents spent 48% of their day, or approximately 11.5 hours, engaged in sedentary activities such as sitting in class, doing homework, commuting, and screen time. In comparison, they spent 33% of their day sleeping, 17% in low-intensity physical activity like casual walking, and only 2% in moderate-to-vigorous physical activities such as running, swimming, or playing basketball.
"I was happily surprised with the strength of the association of replacing 30 minutes of sedentary time with moderate-to-vigorous physical activity - a 15% lower insulin resistance is quite a big change," said Soren Harnois-Leblanc, Ph.D., R.D., lead author of the study and a postdoctoral researcher at Harvard Pilgrim Health Care Institute and Harvard Medical School. "Our findings mean that switching from sedentary behaviors to moderate-to-vigorous physical activity or sleep, even if it is only a few minutes per day to start, was beneficial for health."
Insulin resistance was measured using the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), which estimates resistance based on fasting blood glucose and insulin levels. The study found that while activity composition was associated with insulin resistance, it was not associated with levels of adiponectin or fasting glucose levels. Researchers used statistical modeling to estimate how 30-minute substitutions from sedentary behavior to other activities could affect test results in later adolescence, with results adjusted for factors including age, sex, season, mother's educational level, and family income.
"This study shows that young adolescents spend a lot of their day being sedentary and only a small amount of time being physically active," said Kershaw Patel, M.D., an American Heart Association volunteer and chair elect of the Association's Council on Epidemiology and Prevention. "Interestingly, teens who had more moderate to vigorous physical activity early in adolescence showed signs of lower insulin resistance later on. The big takeaway is being active early in life can really make a difference for long-term health."
The American Heart Association's Life's Essential 8 metrics for optimal cardiovascular health include strategies for incorporating healthy lifestyle into daily life. Recommendations include dimming lights before bedtime, creating nighttime routines without electronic devices, and integrating physical activities with social time to make exercise more appealing than sedentary activities. While the study did not find benefits from light physical activity, researchers noted that "light physical activity is an interesting target because it is likely easier to integrate into everyday routines," according to Harnois-Leblanc.
The study had limitations, including that insulin resistance information in late adolescence was available for only 49% of participants who had accelerometer data collected in early adolescence. Additionally, cause-and-effect for daily activities and insulin resistance cannot be proven by this data analysis. The research is considered preliminary until published as a full manuscript in a peer-reviewed scientific journal. Public health initiatives promoting physical activity or sleep rather than sedentary activities could help preserve cardiometabolic health among teens in the U.S., potentially reducing the growing burden of Type 2 diabetes in younger populations.
