According to the US government's Physical Activity Guidelines for Americans, adults should get at least 150 minutes of moderate-intensity physical activity or 75 minutes of vigorous-intensity exercise every week.
Only one-third of American adults meet the 150-minute-per-week exercise recommendation, per a study in The Lancet.
If scientists and health experts are able to identify the minimum amount of exercise required to decrease mortality risk, more people could potentially be motivated to exercise, some researchers have concluded.
How much exercise you need may not be how much exercise you actually get.
According to the Physical Activity Guidelines for Americans, adults should engage in at least 150 minutes of moderate-intensity physical activity or 75 minutes of vigorous-intensity exercise every week. Put another way, that's 30 minutes of moderate physical activity, 5 days a week.
But what about Americans who exercise yet don’t meet the 150-minute-per-week recommendation? Is there a minimum amount of daily physical activity that still provides health benefits?
The answer: Yes, there is.
Minutes per day add years to life
In a study published in The Lancet, researchers in Taiwan grouped over 400,000 study participants into one of five categories of exercise volume: inactive, low, medium, high, and very high activity. The researchers compared each group with the inactive group, and then calculated each group’s mortality risks and life expectancy.
In comparison with those in the inactive group (who exercised less than 60 minutes per week), people in the low-volume group exercised for approximately 92 minutes per week. This equates to 15 minutes of exercise every day. This group had a 3-year longer life expectancy and a 14% decreased risk for all-cause mortality than the inactive group. These benefits extended to all age groups, both sexes, and to those with cardiovascular disease risks.
In short, just 15 minutes per day of moderate-intensity exercise can have health benefits.
Furthermore, the researchers found that every additional 15 minutes of exercise beyond the minimum 15 minutes per day led to a reduction in general mortality by 4% and a decrease in cancer-related mortality by 1%.
"Individuals who were inactive had a 17% increased risk of mortality compared with individuals in the low-volume group."
— Authors, The Lancet
They study authors noted that only one-third of American adults meet the 150-minute-per-week exercise recommendation and in other countries, such as Taiwan, only one-fifth adhere to these recommendations.
By identifying the minimum amount of exercise that is enough to decrease the risk of mortality, more people could potentially be motivated to exercise, the researchers concluded.
Exercise modestly, at least
Similarly, in a study published in PLOS Medicine that included over 600,000 individuals ranging from 21 to 90 years old age, researchers found that engaging in 75 minutes per week of moderate physical activity, such as taking a brisk walk, led to a 1.8-year increase in life expectancy compared with inactivity.
This equates to exercising for a little over 10 minutes per day and is less than half the amount of daily exercise recommended by the US guidelines. The positive effects seen in life expectancy were also seen in former smokers as well as in African American participants—two groups that have been underrepresented in the literature.
As expected, adhering to or surpassing the 150-minute-per-week guideline led to a 3.4 to 4.5-year increase in life expectancy.
The authors also examined the effect of body mass index (BMI) and physical activity on mortality. They categorized physical activity by metabolic equivalent hours per week (MET-h/wk). Results showed that individuals who were active (7.5 MET-h/wk) and had a normal BMI between 18.5 and 24.9 gained 7.2 years of life in comparison with those who were inactive (0 MET-h/wk) and obese (BMI of 35+).
"These findings suggest that participation in leisure time physical activity, even below the recommended level, is associated with a reduced risk of mortality compared to participation in no leisure time physical activity."
— Authors, PLOS Medicine
“This result may help convince currently inactive people that a modest physical activity program may have health benefits, even if it does not result in weight loss,” the authors added.
A major limitation of these studies is that they rely on self-reporting of physical activity, likely leading to over-reporting of time spent engaging in exercise. However, the data presented has the potential to positively affect global health. These studies suggest that those who engage in physical activity, even if they don’t meet the recommended guidelines, can still reap health benefits, such as a reduced risk of mortality, when compared with those who don’t exercise at all.
If more adults achieve the minimum amount of exercise reported in these studies—which equates to 10 to 15 minutes of moderate activity per day—then mortality from cardiovascular diseases, diabetes, and cancer can be reduced.Read Next: When exercise is bad for your health