New science says this might be the best time of day to exercise

Researchers found evidence that evening exercisers might get better heart and health benefits

New research might help you make the most of your exercising: Scientists tracked the long-term health of people living with obesity and found that those who exercised in the evening were the least likely to experience cardiovascular problems or to die compared to non-exercisers and those who exercised at other times.

There has been a long-running debate over whether physical activity can be more beneficial at certain times of the day. Our bodies have an internal clock, or circadian rhythm, which subtly affects our mood, metabolism, body temperature, and many other things, so it’s plausible that timing could affect the gains we get from exercising. The scientific verdict has been mixed, though. While many studies have suggested that afternoon to evening exercise seems better overall, there have been others backing the added value of a morning routine.

This new study was led by researchers at University of Sydney in Australia, who had access to data from the UK Biobank, an extensive research project that has followed UK residents’ health for many years. The team focused on a subset of about 30,000 volunteers living with obesity over the age of 40, who had no pre-existing cardiovascular disease. As part of the original study, these volunteers had agreed to wear activity trackers for a week.

They used these measurements as a proxy for people’s typical level of physical activity. They identified people who engaged in moderate to vigorous aerobic physical activity (defined as bouts of intense physical activity that lasted at least three minutes at a time), then split these volunteers into those who tended to exercise in the morning, afternoon, or evening (after 6 p.m.). For a baseline reference, they used people who barely exercised at all, meaning they averaged less than one bout of intense physical activity a day.

The volunteers were tracked for nearly eight years on average. Compared to the baseline of no exercise, and after accounting for other factors like age or smoking history, people who exercised in the morning or afternoon were still better off, the researchers found. But it was ultimately evening exercisers who had the lowest risk of developing cardiovascular disease and of dying in general. And this same pattern held true when the researchers only looked at the subset of people with type 2 diabetes.

The findings, published in the journal Diabetes Care, are still observational, meaning that they can’t prove a cause-and-effect link between evening exercise and better health. And as the study itself indicates, regular exercise is good for your heart and health no matter when it happens. Some recent research has also suggested that exercise in the morning may have its own unique benefits, such as better fat-burning. But the authors say their findings, if further confirmed, could help those looking to optimize their cardio routine, especially if they’re living with obesity or diabetes. “Timing of physical activity may play a role in the future of obesity and T2D management,” they wrote.