Exercising after lunchtime the sweet spot to cut blood sugar

A study of people with type 2 diabetes showed benefits were about 50 per cent greater for those who exercised from 1.45pm to 5pm.

Physical exertion at certain points in the day improves the chance of lowering blood sugar. Picture: Getty Images

People with type 2 diabetes should exercise in the afternoon instead of the morning to best control their blood sugar, research suggests.

A team at Harvard Medical School looked at 2416 patients, who were all urged to adopt healthier lifestyles. Participants were divided into groups based on when they were most active – morning, midday, afternoon or evening – and wore Fitbit-style devices which measured activities such as running, swimming or gardening.

Exercise helped all the patients lower their blood sugar levels, but the benefits were about 50 per cent greater for those who exercised between 1.45pm and 5pm.

Blood sugar levels tend to peak after lunch, meaning that afternoon exercise pays off. Picture: Getty Images

The patients, who were all overweight and had type 2 diabetes, were monitored for four years. Afternoon exercise had the greatest long-term benefits, with this group less at risk of complications and more likely to be able to come off medication.

Jingyi Qian, the study’s author, said: “We’ve known that physical activity is beneficial, but what our study adds is a new understanding that timing of activity may be important too.”

Part of the explanation is that afternoon exercise reduces the peak in blood sugar levels after eating lunch. Blood sugar usually spikes an hour or two after eating meals as the body digests carbohydrates, but exercising means muscle cells burn the glucose this creates. Managing post-meal spikes helps to keep blood glucose levels stable over the long term.

The study, published in the journal Diabetes Care, added that the circadian rhythm, or body clock, means that the body’s response to exercise varies depending on the time of day as hormone levels fluctuate. It concluded that encouraging patients to prioritise the afternoon for exercise was a “promising” way to manage diabetes.

More than five million people in the UK have diabetes, which occurs when a person’s blood sugar becomes too high as the body stops producing or responding to the hormone insulin.

Lucy Chambers, head of research communications at the charity Diabetes UK, said: “Keeping physically active can help people with type 2 diabetes manage their blood sugar levels and reduce their risk of developing serious diabetes-related complications such as heart disease and kidney failure, as well as improving wellbeing.

“This new research found that regular ‘moderate-to-vigorous’ physical activity – whether in the morning, midday, afternoon or evening – was associated with lower average blood sugar levels in people with type 2. Afternoon exercise was linked with the greatest benefits but the reasons for this are unclear and current evidence on optimal times for exercising is mixed.

“If you’re living with type 2 diabetes, the most important thing is to find an exercise you enjoy and that you can incorporate into your routine in the long term.”

The NHS encourages patients with type 2 diabetes to try to exercise for at least 2½ hours each week. Exercise increases insulin sensitivity, which helps cells use any available insulin to take up glucose from the blood.

Rising obesity means that by 2030 one in 10 adults is expected to have type 2 diabetes, which can cause complications such as eye problems and lead to foot amputations.

Type 2 diabetes is linked to obesity, while type 1 is an unpreventable auto-immune condition that is usually diagnosed in childhood.

The Times