My guilty pleasure is Quora, which I dip into if a question intrigues me. Sometimes I “archive” the more interesting topics here.
“Is walking for 45 minutes a day enough to not have a sedentary lifestyle if you sit behind a desk for 7 hours a day?“
Medically, we don’t really have a clear, single definition of “sedentary lifestyle,” beyond knowing that a society in which a large number of people work in a sitting position means people do need to make purposeful effort to ensure they have adequate movement during the day. Most studies and government-issued guidelines around sedentary behavior cite health risks as being more common above a threshold of around … 7 hours a day (perhaps the reason you mention that number), although some suggest it is lower.
There are, of course, definitions of sedentary behaviors, and there are studies of health outcomes with respect to different kinds of sedentary behaviors. For example, there is research showing that hours of television watching is associated with poorer health outcomes, but the evidence for sitting to do other activities “behind a desk” (more cognitively demanding, such as work or using a computer for something other than just watching video) is not as negative, so we can’t even necessarily think of the mere fact as sitting across time as defining a “sedentary lifestyle.”
In the US, the guideline for adequate weekly activity to improve health outcomes works out to about 25 minutes a day of walking – less for vigorous exercise like running. The data we do have about exercise indicates that health benefits continue to accrue as exercise level increases, to a point that far exceeds 45 minutes a day. For people who like evolutionary explanations, investigators who work with societies that still practice hunter/gatherer lifestyles tend to find they are active on the order of 3 to 5 hours a day, of which over an hour is moderate to vigorous physical activity, so about triple the recommended level, and almost double 45 minutes a day. Very importantly, their activity levels don’t drop off with age as much as the activity levels of people living in westernized societies; they remain quite active throughout the life course.
This still leaves us with the question of what we should aim for. Studies that look for associations with better outcomes at different levels of steps per day keep finding more up to about 16,000. At that level, it’s hard to analyze effectively because there are not enough people who do it, or not enough people with different characteristics who do it. For example, it is possible that people who routinely walk more than 2 hours a day are different in many ways from people who walk 5,000 to 10,000 steps a day, and so it would not be possible to compare the two groups solely on the basis of walking volume.
From what we do know, 45 minutes a day, assuming that covers at least 5000 steps, will certainly be helpful, and it greatly exceeds the US activity guidelines (which are more of a starting point than a limit). More is almost always better. From a healthy aging perspective, being active consistently and daily – and including some strength training – is a key to a higher quality of life, and greater independence, for longer.