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The specific benefits of different amounts of physical activity are not completely clear

It should be commonly known by now that being physically active on a regular basis is beneficial and has a protective effect against many diseases and health conditions. Despite this, it's not completely clear how this protective effect differs based on the exact amount of physical activity an individual gets. In other words, what amount of physical activity is necessary to experience specific effects, and how does this change with greater amounts of activity? The World Health Organization (WHO) currently recommends getting 600 metabolic equivalents (MET) minutes of total activity each week in order to obtain health benefits. A MET is a unit of measurement used to describe the amount of energy exerted when performing physical tasks or activities, and 600 MET minutes in a week is approximately equal to walking (4 METs) for 150 minutes or running (8 METs) for 75 minutes total. Totals for MET-minutes are calculated by multiplying the METS for the activity by the number of minutes it's performed, so five hours of gardening (4 METs) in a week equates to 4 x 300 = 1,200 MET minutes. Though these values are commonly used for physical activity recommendations, it's not completely understood to what degree they reduce the risk for certain health conditions and if greater amounts reduce this risk even more. Therefore, a powerful pair of studies called a systematic review and meta-analysis was conducted. The systematic review gathered all of the highest-quality evidence on the topic available, and the meta-analysis compared the findings of these studies to one another to establish a conclusion.

Researchers identify 174 studies for the systematic review and meta-analysis

Researchers searched through two databases for studies that examined the connection between physical activity and the risk of any of the following five health conditions: breast cancer, colon cancer, diabetes, heart disease and stroke. In particular, they were interested in the total MET-minutes per week of individuals and how that affected their risk for any of those five conditions. After screening 6,965 studies, researchers identified 174 that fit the necessary criteria and were used for the meta-analysis.

Risk for disease is lowered with more physical activity, but only to a certain point

Results from the meta-analysis showed that higher levels of total physical activity were associated with a lower risk for all five of the health conditions that were looked into. The health benefits that individuals experienced were found to be the greatest once achieving a certain amount of physical activity, but after that point, the decrease in risk for the conditions studied was minimal. One of the main examples to illustrate this point is the following: individuals who got 600 MET-minutes per week of physical activity had a 2% lower risk of diabetes compared with those who did not get any physical activity. When the amount of physical activity increased from 600 to 3,600 MET minutes/week, this risk was reduced by an additional 19%. After this, however, similar increases in physical activity only led to small reductions in the risk for diabetes. Similar trends were found with the other health conditions examined as well.

Individuals should get more physical activity than what is recommended

Based on this, researchers said that getting 3,000-4,000 MET-minutes per week appears to be the ideal range for obtaining the most health benefits and the greatest reduction of risk for the five health conditions. More physical activity than this may not necessarily lead to more benefits or a lower risk. The researchers, therefore, suggest that the physical activity levels of individuals should be significantly higher than what is currently recommended (600 MET-minutes/week) in order experience the greatest reduction in risks for breast cancer, colon cancer, diabetes, heart disease and stroke. Since it may take some time before any recommendations are actually changed, individuals can take matters into their own hands and work towards getting more physical activity for their overall health and risk for a disease.