Recent research from CU Boulder and the University of California, Riverside, reveals that millennials are spending over 60 hours a week sitting due to long commutes, back-to-back Zoom meetings, and evenings spent streaming and scrolling through social media. This sedentary lifestyle could increase their risk of heart disease and accelerate other signs of ageing.
The study of over 1,000 individuals from Colorado, including 730 twins, is one of the first to investigate how prolonged sitting affects health metrics such as cholesterol levels and body mass index (BMI) in young adults.
Research shows that simply meeting the minimum physical activity guidelines—approximately 20 minutes of moderate exercise each day—is insufficient to offset the risks associated with spending most of our waking hours sitting.
“Our research indicates that reducing the sitting time during the day, engaging in more vigorous exercise, or implementing a combination of both may be essential for lowering the risk of premature ageing in early adulthood,” stated the study’s senior author, Chandra Reynolds, a professor in the Department of Psychology and Neuroscience as well as the Institute for Behavioral Genetics.
After the COVID pandemic, Bruellman noticed that he and others his age were sitting more. He set out to learn more about the consequences.
“Young adults often believe they are immune to the effects of aging. They think, ‘My metabolism is excellent, so I don’t need to worry until I reach my 50s or 60s,’” said Bruellman. “However, what you do during this crucial stage of life is important.”
A walk after work isn’t enough.
The authors analyzed data from participants aged 28 to 49, with an average age of 33, from CU’s Colorado Adoption/Twin Study of Lifespan Behavioural Development and Cognitive Ageing (CATSLife), which has followed twins and adopted individuals since Childhood.
Participants reported sitting almost 9 hours daily, with some sitting as much as 16 hours. On average, they reported between 80 and 160 minutes of moderate physical activity weekly and less than 135 minutes of vigorous exercise weekly. The authors note that these results are likely better than national averages due to Colorado’s active lifestyle.
The researchers looked at two key heart and metabolic ageing measures: total cholesterol/high-density lipoprotein and body mass index (BMI). The study found that the more one sat, the older one looked. Adding a little moderate activity on top of a long day of sitting did little to buffer these impacts.
Young adults who sat 8.5 hours per day and performed at or below current exercise recommendations could enter a “moderate to high risk” category for cardiovascular and metabolic disease, the authors said.
“Taking a quick walk after work may not be enough,” said Reynolds. “While this is increasingly apparent with age, we show that associations are already emerging in early adulthood.”
Adding vigorous activity did have a buffering effect.
For instance, those who exercised vigorously (think running or cycling) for 30 minutes daily had cholesterol and BMI measures that looked like those of individuals five to 10 years younger who sat as much as they did but didn’t exercise.
However, even vigorous activity could not fully buffer the negative impacts of prolonged sitting, the study concluded.
Same genes, different lifestyles
Identical twins are handy to study because they share 100% of their genes, making it easier to rule out genetic factors that might contribute to different health outcomes and zero in on lifestyle differences.
When looking at a subset of twins with different sitting and physical activity habits, the researchers found that replacing sitting with exercise seemed to improve cholesterol better than simply adding exercise to a full day of sitting.
The bottom line, the researchers said, is to try to do both.
To reduce sitting time at work, use a standing desk, take breaks, and organize walking meetings. If possible, do something that gets you out of breath for at least 30 minutes per day, or be a “weekend warrior” and get in longer, vigorous workouts when you can, said Bruellman.
He hopes the study will prompt policymakers to revisit physical activity guidelines and specify how much sitting is too much.
Meanwhile, Reynolds encourages young adults to take steps now that could shape their future:
“This is the time to build habits that will benefit health over the long term.”