David Keisler

David Keisler

A recent study published in the April 2019 issue of The Journal of Applied Physiology was brought to my attention by reading the comments of NYT columnist Gretchen Reynolds. There is now some evidence to support the fact that prolonged sitting is not only unhealthy but also excessive sitting could cause resistance to the benefits of exercise.

Those who exercise on a regular basis are known to have a lower incidence of developing heart disease and Type II diabetes. A single workout helps to improve metabolism after meals and promote favorable insulin levels. A sedentary life style has the opposite effect especially relative to insulin resistance and abnormal blood sugar levels. Therefore excessive sitting could negate the beneficial effects of exercise.

In this study, 10 fit men and women were asked to take less than 4,000 steps per day and sit for at least 13 hours daily. They were prescribed a healthy diet with fewer calories to avoid weight gain. On day five, after a calorie-dense breakfast blood measurements of glucose, triglycerides and insulin levels were followed for the next six hours. As expected, these levels were elevated compared to baseline studies.

The same group was again restricted to the sedentary rules of less than 4,000 steps per day and sitting for 13 hours. However, on day four, they were asked to exercise on a treadmill for one hour. On day five, after the same breakfast as before was eaten, the same blood chemistries were followed for the next six hours. Unfortunately those blood chemistry levels were no better on the fifth day. The hour of exercise on day four did not have beneficial effects noted on day five.

The author's conclusion was that prolonged sedentary time may cause resistance to the benefits of exercise. This is not good news for those who exercise regularly yet who are also sedentary for long periods of time such as sitting at a desk. Prolonged sedentary time such as 13 hours per day may somehow cause resistance to the benefits of one hour of exercise.

It has been said before that sitting is the new smoking. It is recommended that if you are desk-bound by necessity, try to take a standing break every 30 minutes or so and walk around for a few minutes. Consider using a desk that allows you to stand up and work from a standing position. Look at a desk and chair as a ball and chain. Break the chain by standing at intervals, and try to take at least 10,000 steps a day.

Better yet, consider becoming a nurse. You will hardly ever have time to sit down on the job and you will be on your feet for the entire shift. One of my nurse friends just completed the Boston Marathon and the other has finished several triathlons and numerous road races. Congratulations to both of you.

David KeislerĀ is a gastroenterologist and internist in Aiken.