People with obesity may benefit most when exercise is done in the evening

New research suggests the best time of day for people with obesity to exercise is between 6 p.m. and midnight.

In a study of nearly 30,000 adults with obesity, people who worked out in the evenings had the lowest risk of premature death, cardiovascular disease and microvascular disease – a type of heart disease. The frequency in which people engaged in at least three minutes of moderate-to-vigorous physical activity also may be more important than their total daily amounts of physical activity.

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"Exercise is by no means the only solution to the obesity crisis, but this research does suggest that people who can plan their activity into certain times of the day may best offset some of these health risks," said researcher Angelo Sabag, of the University of Sydney in Australia. The study was published last week in the medical journal Diabetes Care. 

The researchers said more studies are needed to establish causal links, but their findings potentially could influence future preventative health care recommendations.

Though this study specifically looked at people with obesity, other research on the best time to exercise has considered the overall population. A 2019 study found that evening exercise may help people fall asleep faster and spend more time in deep sleep – as long as the person does not engage in high-intensity exercise, like interval training, less than an hour before bedtime. 

Another 2019 study found mid-morning exercise is the best for metabolic health. Research published last year found that people who were physically active between 11 a.m. and 5 p.m. were less likely to die early of heart disease and other causes, excluding cancer.  

The researchers said they did not just track "structured" exercise. Rather, they focused on tracking continuous aerobic activity in bouts of three minutes or more due to previous research demonstrating a strong association between this and better glucose control and a lower risk of cardiovascular disease.

"We didn't discriminate on the kind of activity we tracked, it could be anything from power walking to climbing the stairs, but could also include structured exercise such as running, occupational labour or even vigorously cleaning the house," researcher Matthew Ahmadi said.

During the eight-year follow-up period, researchers recorded 1,425 deaths, 3,980 cardiovascular events and 2,162 microvascular dysfunction events, which causes the small blood vessels feeding the heart muscle to not work as they should.