When it comes to exercise and longevity, timing may be very important.

A new and very large international study published this week in the journal Nature Communications says when you exercise or engage in other moderate-to-vigorous physical activity may help determine the health benefits.

Afternoon physical activity appears to offer the greatest benefit.

The study used data from 92,139 UK Biobank participants and was led by researchers at Guangdong Cardiovascular Institute in China and included researchers from other parts of China and from Sweden.

Among the findings:

  • Physical activity is good, regardless of when you do it. The study said, “Moderate-to-vigorous intensity physical activity at any time of day is associated with lower risks for all-cause, cardiovascular disease and cancer mortality.”
  • Afternoon (11 a.m. to 5 p.m.) and mixed-timing exercise — basically not sticking to a set schedule — “have lower risks of all-cause and cardiovascular disease mortality” compared to morning (5 a.m. to 11 a.m.) and evening (5 p.m. to midnight) exercise.
  • Exercise regardless of time of day lowered the risk of dying from cancer.

About the study

Accelerometers, which track activity, were used for seven days to measure when and how intensely people work out and when they tend to do so.

After an average of seven years, they looked at death records. Among participants, about 3,000 had died — about a third from heart disease and nearly two-thirds from cancer. Roughly 200 died of other causes.

The association between timing and death risk was “independent of sociodemographic factors, lifestyle, other health impacts, sleep duration, sleep midpoint and the volume of moderate-to-vigorous physical activity,” the study authors wrote.

The protective effect of exercising in the afternoon hours was greatest for older adults, males, less active individuals and those with preexisting heart disease.

The researchers described their findings as “robust.”

It’s worth noting moderate-to-vigorous activity is a broader category than deliberate, targeted exercise.

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While the researchers cited several advantages to the study, they also noted some limitations, including the fact that the UK Biobank sample is generally healthier and live in a more socioeconomically secure area than the average person. And because the study was observational, it didn’t prove causation.

Exercise always matters

But don’t count out exercising at other times of day. Insider, reporting on the new study, said that “Prior research has found morning workouts can help cut fat, while evening exercise may improve mood.”

The study on burning fat came out of the Karolinska Institute and the University of Copenhagen, using mice to demonstrate an increase in fat metabolism.

Morning workouts also reduce blood pressure.

“The ideal time of your workout might depend on your goal, as a small study from 2022 found morning exercise helped women cut down on belly fat and blood pressure, while afternoon lifts increased muscular strength and mood,” Insider reported.

According to Metro UK, the afternoon exercise “also happens to coincide with the time of day that people are statistically less likely to have a heart attack.”

A fitness expert and physical therapist, Ben Dillon, told Metro that “studies have also shown that physical performance is at its peak during the late afternoon, meaning you may be able to work out harder and longer, which can lead to better results.” He added, “Afternoon workouts can help reduce stress levels, ease tension and promote relaxation, which may aid in recovery post-workout.”