A little exercise goes a long way, a new study suggests. So little that 15 minutes of it per day reduces one's risk of cancer and adds an average of three years to a person's life.
Taiwanese researchers examined more than 400,000 study participants in a 12-year period, where patients self-reported their weekly exercise regimen and were then placed in one of five groups: inactive, low, medium, high or very high exercise activity.
The study, published in this week's Lancet, found that people in the low-exercise group averaged 15 minutes of fitness per day. They reduced their risk of dying from cancer by 10 percent and had a three-year longer life expectancy than the inactive group.
"The 30-minute a day for five or more days a week has been the golden rule for the last 15 years, but now we found even half that amount could be very beneficial," said Dr Chi-Pang Wen, lead author of the study. "As we all feel, finding a slot of 15 minutes is much easier than finding a 30-minutes slot in most days of the week."
With every additional 15 minutes of exercise per day, participants reduced their risk of dying from cancer by another 1 percent. Wen did not encourage those who follow the "golden rule" of 30 minutes of fitness per day to cut back on their exercise, but he did hope that the findings encourage inactive people to get moving.
"To get started by the inactive is the most difficult challenge or make the couch potato move the first step," Wen said. "We hope this 15-minute message can facilitate the inactive into moving ... the inactive constituted the majority worldwide."
In the study, low levels of fitness represented 15 minutes of moderate-intensity exercise, which was described as any activity that makes a person short of breath, but able to carry on a conversation. Examples of such exercises included brisk walking, easy jogging, biking and ballroom dancing.
While the study was based in Taiwan, Wen said he believes the results "can be universally applied."
"Many studies have been performed in different countries in individuals with different ethnic backgrounds to evaluate the health benefits of exercise," said Dr. Anil Nigam, associate professor of medicine at University of Montreal, who also wrote the editorial for the study. "The results are generally quite consistent. Therefore, we have no reason to doubt that similar benefits are achievable in the North American context."
But experts were also quick to point out caveats.
The study was based on self-reported data, which often leaves a margin of error. Some experts also noted the difficulty in determining the cause and effect behind the study.
"Do inactive people live shorter lives, and get more cancer, because of their inactivity?" said Dr. Daniel Blumenthal, chair of the department of community health and preventive medicine at Morehouse School of Medicine in Atlanta. "Or are they inactive because they are ill [perhaps they are getting cancer] and it is this illness that leads to their earlier death? Does inactivity lead to illness, or does illness lead to inactivity?"