Research has repeatedly shown that regular physical activity is necessary not just for maintaining our physical fitness, but also for keeping us healthy.
What the studies (and the experts) don’t agree on, however, is how much or how strenuous that exercise needs to be to make a difference, specifically when it comes to reducing our risk of heart disease, diabetes and other chronic diseases.
But the study also offers some reassuring news: That activity does not have to be in the form of “leisure time” exercise, such as running or playing tennis or purposeful brisk walking. Being more active in ordinary daily life “domains”— cleaning the house, for example, or gardening, or doing errands on foot or on a bicycle — can also help us lower our risk of disease.
That is, as long as we do enough of it.
For the study, a team of U.S. and Australia researchers conducted a meta-analysis — a detailed examination of data from 174 previous studies published between 1980 and 2016. Each of these studies had examined the possible relationship between total physical activity (not just leisure forms of exercise) and at least one of five chronic diseases: coronary heart disease, stroke, diabetes, breast cancer and colon cancer.
They found that physical activity was associated with a lower risk of all five chronic diseases. But that drop in risk became significant only when the physical activity reached levels higher than the 600 metabolic equivalent (MET) minutes per week recommended by the World Health Organization (WHO).
Indeed, the analysis found that the risk of developing the five chronic diseases — particularly heart disease and diabetes — dropped significantly when physical activity reached a minimum of 3,000 to 4,000 MET minutes per week.
For example, engaging in a total of 600 MET minutes per week was associated with a 2 percent lower risk of diabetes (compared to not doing any physical activity at all). But upping that physical activity to 3,600 MET minutes per week reduced the risk by an additional 19 percent.
When physical activity levels exceeded 3,000 to 4,000 MET minutes per week, however, there were diminishing returns. The risk of diabetes fell by only an additional 0.6 percent, for example, at 9,000 to 12,000 MET minutes per week.
And what exactly is a MET minute? In simplest terms, it’s the amount of energy, or calories, expended while sitting quietly. So, here’s how to translate the study’s numbers into something meaningful: 600 MET minutes would be the equivalent of about 150 minutes per week of moderate activity (such as brisk walking) or 75 minutes of intense activity (such as running).
Reaching 3,000 MET minutes a week would, therefore, require a much greater effort — but not necessarily by training for a triathlon.
“A person can achieve 3,000 MET minutes per week by incorporating different types of physical activity into the daily routine,” said lead author Hmwe Kyu of the University of Washington’s Institute of Health Metrics and Evaluation in Seattle, in a released statement. “For example, climbing stairs for 10 minutes, vacuuming for 15 minutes, gardening for 20 minutes, running for 20 minutes, and walking or cycling for transportation for 25 minutes, on a daily basis, would together achieve about 3,000 MET minutes a week.”
Limitations and implications
This meta-analysis is based on observational studies, and therefore can’t prove a relationship between the amount and/or type of physical activity and a lowering of the risk of chronic disease.
Still, Kyu and her co-authors believe their findings strongly suggest, as has much previous research, that all activity counts.
“More studies using the detailed quantification of total physical activity will help to find a more precise estimate for different levels of physical activity,” they acknowledge. Yet that shouldn’t stop public health officials, lawmakers and others from creating and implementing policies that make it easier for more people to become physically active.
“With population ageing, and an increasing number of cardiovascular and diabetes deaths since 1990, greater attention and investments in interventions to promote physical activity in the general public is required,” they write.
Bottom line: Stay physically active, in whatever way you can.
FMI: You can read the study in full on the BMJ website.