Ask the Doctors: Even minimal exercise helps reduce health risks from sedentary lifestyle

Dear Doctors: I saw on the news that, if you work out for 11 minutes a day, you are protected from the bad stuff that happens from sitting too much. Is that really true? I’m stuck at my desk all day.

Dear Reader: A study published in the British Journal of Sports Medicine looked at health outcomes of people whose lifestyles ranged from extremely sedentary to moderately active and found that even a small amount of daily exercise helped mitigate the negative health effects of prolonged inactivity.

Several years ago, research linked prolonged sitting — that’s eight hours or more a day — to increased risk of premature death. With so many jobs now tethering workers to their desks, people have become eager to learn how to lessen the ill effects.

This new research, which reexamines data from nine studies, focused on about 44,000 people who wore an activity tracker to accurately monitor daily movement. The participants, middle-aged and older, remained seated an average of 10 hours a day. When they exercised, it consisted of short sessions — eight to 35 minutes — often walking at a moderate pace.

When the researchers looked at mortality rates in the years after the participants enrolled in the studies, they found the expected link between people who exercised the least and an increased risk of premature death.

The surprise was just how much exercise it took to reverse the trend toward earlier death. The answer: 11 minutes daily.

It’s important to note that those 11 minutes of exercise did not completely erase the ill effects of prolonged sitting. But the study suggests that even a small amount of exercise appears to have benefits.

The magic number when it comes to exercise actually appears to be 35. The greatest benefit comes from doing moderate exercise at least 35 minutes daily — in line with federal guidelines for at least 150 minutes of moderate aerobic activity, or 75 minutes of vigorous aerobic activity, spread over the course of a week.

Several studies have suggested that those 35 minutes of exercise don’t have to happen all at once. They can be split up into several sessions and still yield a similar benefit.

That’s encouraging for people who think they don’t have time to exercise.

Dr. Eve Glazier and Dr. Elizabeth Ko are internists at UCLA Health.