It’s been said that the “sitting disease” harms health as much as smoking.
But does excessive sitting also affect young people’s health?
Research findings from the University of Colorado Boulder and the University of California Riverside reveal that millennials are spending more than 60 hours a week sitting — whether due to long commutes, video conference-packed workdays, or evenings spent streaming and scrolling.
This extended sitting time could be raising their risk for heart disease and accelerating other signs of aging.
The study, which analyzed data from over 1,000 Colorado residents, including 730 twins, is one of the first to examine how prolonged sitting affects critical health markers like cholesterol levels and body mass index (BMI) in young adults.
The research suggests that meeting the current physical activity guidelines — about 20 minutes of moderate exercise per day — may not be enough to counteract the health risks associated with sitting for long hours.
“Our research suggests that reducing sitting time, increasing vigorous exercise or a combination of both may be necessary to reduce risk of premature aging in early adulthood,” explains Chandra Reynolds, senior author of the study; professor in the Department of Psychology and Neuroscience at CU Boulder.
The Health Impact in Younger Adults of Sitting for too Many Hours
The study, published in PLOS ONE (2024), was led by Reynolds in collaboration with Ryan Bruellman, a doctoral candidate at UC Riverside.
After noticing an increase in sitting time following the COVID-19 pandemic, Bruellman decided to investigate the long-term effects of prolonged sitting on young adults.
Young adults often believe that they’re immune to the effects of aging, says Bruellman in the paper.
But young adulthood is a very important time to think about what you do as far as lifestyle habits, because what the young adult does NOW will have a great impact later on.
Participants in the study ranged from 28 to 49 years old, with an average age of 33.
On average, they reported sitting for almost nine hours daily, with some sitting as much as 16 hours.
Despite this, they still engaged in moderate physical activity for about 80 to 160 minutes per week and less than 135 minutes of vigorous exercise.
Notably, these results were likely better than the national average due to Colorado’s active lifestyle.
The Study Findings: Sitting Time and Early Aging
The researchers examined two key health markers that reflect heart and metabolic aging: total cholesterol and high-density lipoprotein (HDL) levels, as well as BMI.
The study found that the more participants sat, the older their heart and metabolic health appeared.
Adding some moderate physical activity, such as a walk after work, did little to offset the negative effects of prolonged sitting.
In fact, the study revealed that young adults who sat for about 8.5 hours per day and followed current exercise recommendations were at “moderate to high risk” for cardiovascular and metabolic disease.
Thus, a brisk walk after work may not be sufficient, says Reynolds in the report.
The effects of prolonged time in a chair are already noticeable in younger adults.
Vigorous Exercise Helps, but Doesn’t Fully Offset Sitting
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While moderate activity didn’t seem to mitigate the risks of sitting, adding vigorous exercise did make a significant difference.
Participants who engaged in 30 minutes of vigorous exercise daily — such as running or cycling — had cholesterol and BMI levels similar to those of individuals five to 10 years younger, even if they sat as much as their peers.
However, the study concluded that even vigorous exercise couldn’t completely negate the negative impacts of prolonged sitting.
The Role of Genetics and Lifestyle
The study also focused on a subset of identical twins, who share 100% of their genes.
This allowed the researchers to isolate lifestyle factors, such as sitting and physical activity, and examine their impact on health outcomes.
The results showed that replacing sitting with exercise worked better to improve cholesterol levels than simply adding exercise to a day full of sitting.
What Can You Do?
The bottom line, according to the researchers, is to try to do both: reduce sitting and get more vigorous exercise.
For those who work in offices, the researchers suggest using a standing desk, taking regular breaks and organizing walking meetings.
If possible, aim for at least 30 minutes of vigorous activity daily or become a “weekend warrior” by fitting in longer workouts on your days off.
Another very effective option is to get a treadmill desk for home use.
Lorra Garrick is a former personal trainer certified through the American Council on Exercise. At Bally Total Fitness she trained women and men of all ages for fat loss, muscle building, fitness and improved health.
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