Sitting Too Much Raises Cancer Risk, But Short Bursts of Light Activity May Help

• A new study found that prolonged sedentary behaviors can raise the risk of various cancers, including colorectal, pancreatic, and breast cancer. 
• Replacing just 1 hour of prolonged sedentary behavior per day with light physical activity reduced the risk of cancer death by 12%. 
• While the findings don’t establish causality, they can help guide personalized strategies to break up sitting time. 

Sedentary behaviors are ubiquitous in modern life. Many jobs require long periods of sitting, and many people enjoy streaming television shows and movies or playing video games. Whatever the reason, a sedentary lifestyle may raise the risk of various health issues. 

A new study published in PLOS Medicine on July 2 found that prolonged sedentary behavior could increase the risk of many types of cancer. 

However, the findings also indicate that breaking up your sitting time, even with just an hour of light activity, can greatly reduce the risk. 

“A sedentary lifestyle can lead to a person becoming overweight,” said David Yashar, MD, hematologist-medical oncologist of MemorialCare Todd Cancer Institute at Long Beach Medical Center in Long Beach, CA. Yashar wasn’t involved in the study.

“We know that an increased amount of fat causes inflammation, which is a known risk factor for cancer. Obesity has also been associated with the development of colorectal cancer,” Yashar told Healthline.

Prolonged sitting raises cancer-related death risk by 10%

The study analyzed data from 91,292 participants in the UK Biobank. Each participant had worn an activity monitor for 7 days and was followed for an average of 12.38 years afterward. 

During the study, activity was categorized in the following ways: 

• prolonged sedentary (bouts of at least 30 minutes, with at least 90% of the time sedentary) 
• interrupted sedentary (lasted less than 30 minutes or was broken up with more than 10% non-sedentary time)
• varying degrees of physical activity

Yashar explained that sedentary lifestyles may lead to hormonal imbalances that may contribute to the development of certain hormone-sensitive cancers, such as breast cancer.

Prolonged sedentary behavior was associated with a higher risk of cancer death and overall cancer incidence. It was associated with cancers, such as: 

• colorectal cancer
• breast cancer
• liver cancer
• kidney cancer
• pancreatic cancer
• ovarian cancer
• esophageal cancer
• thyroid cancer 

For each additional hour of uninterrupted prolonged sedentary behavior, there was a 10% higher risk of cancer-related death. 

Light physical activity reduces cancer death risk by 12%

Current guidelines recommend 150 minutes of moderate-intensity activity each week. However, this study shows that even light-intensity activity can lower your cancer risk. 

The researchers found that replacing at least 1 hour of daily prolonged sedentary behavior with light physical activity can reduce the risk of cancer death by 12%. 

“Our findings suggest that the health effects of sedentary behavior may depend not only on total sedentary time, but also on whether that time is accumulated in prolonged bouts or interrupted by activity,” the study authors said in a press release. 

“This pattern is biologically plausible: experimental studies have shown that interrupting prolonged sitting with short bouts of activity can improve metabolic responses compared with uninterrupted sitting.”

According to the United Kingdom’s National Health Service (NHS), light physical activity is anything that involves moving rather than sitting or lying down. 

Light physical activity may include: 

• getting up to get a drink
• moving around your house
• walking at a slow pace
• cleaning and dusting
• vacuuming 
• making your bed
• standing up

Regular physical activity can benefit your health in many ways. Moderate-intensity activity may provide more benefits. However, it is important to remember that some movement is better than none. Breaking up your sedentary time with light activity can be a good stepping stone to more vigorous activity.