Doing most of your exercise in the evening “is linked to the greatest health benefits for people living with obesity”, according to a new study from the University of Sydney.

It also suggests, in line with previous research, that evening exercise is the most protective against type 2 diabetes.

Two-thirds of Australian adults are overweight or obese, while one in four of our children and teens are overweight or obese.

Meanwhile, the rate of type 2 diabetes has tripled in Australia over the past 30 years. This has occurred in line with the obesity epidemic.

It’s a looming nightmare for our ageing population.

The Sydney study followed the health trajectory of 30,000 people over almost eight years.

According to a statement from Sydney’s Charles Perkins Centre:

• The researchers used data from UK Biobank and included 29,836 adults aged over 40 years of age living with obesity, of whom 2995 participants were also diagnosed with type 2 diabetes
• Participants were categorised into morning, afternoon or evening moderate to vigorous exercisers. This was based on when they undertook the majority of their aerobic exercise as measured by a wrist accelerometer worn continuously for 24 hours a day over seven days
• Health data from the National Health Service and National Records of Scotland allowed the researchers to follow participants’ health trajectory for 7.9 years
• Over this period they recorded 1425 deaths, 3980 cardiovascular events and 2162 microvascular disfunction events.

The researchers found that those who did the majority of their aerobic moderate to vigorous physical activity – the kind that raises our heart rate and gets us out of breath– between 6pm and midnight had the lowest risk of premature death and death from cardiovascular disease.

Importantly, the study didn’t just track structured exercise.

Dr Matthew Ahmadi, joint first author and National Heart Foundation postdoctoral research fellow at the Charles Perkins Centre, said: “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.”

Instead, researchers focused on “tracking continuous aerobic MVPA in bouts of three minutes or more”.

Previous research “shows a strong association between this type of activity, glucose control and lowered cardiovascular disease risk compared with shorter (non-aerobic) bouts”.

Previous research supports the findings

As we reported in 2021, a small study from the Australian Catholic University looked at a group of men who were on the brink of tipping into diabetes.

These men were fat and loath to get moving – which accounts for three out of four of us.

The participants were aged between 30 and 45 with a BMI ranging from 27 to 35 kg/m2, did not have known cardiovascular disease or type 2 diabetes, and were not taking prescription medications or undertaking shift work.

Pushing the point, the researchers put all 24 participants on a high-fat diet for 11 days.

The men were split into three groups in which they exercised in the morning, the afternoon or not at all.

After five days, the men who exercised in the morning enjoyed a lift in cardiorespiratory fitness.

Otherwise they were equal with the no-movement control group. They had unhealthy cholesterol levels, blood-sugar chaos, and molecular signals of impending heart disease and a metabolic slump.

In other words, they were in worse shape than when they started the study.

For those who exercised in the evening, it was a happier story.

Their fasting blood glucose, insulin, cholesterol, triacylglycerol and LDL-cholesterol concentrations all decreased.

That is, their metabolic health improved, and their risk of type 2 diabetes dropped.