- The timing of exercise may influence blood sugar levels in people with type 2 diabetes, a new study finds.
- People who worked out in the afternoon were more likely to have lower blood sugar levels.
- Experts stress that working out any time of day is important for diabetes management.
Exercise is a helpful tool in managing blood sugar for people with type 2 diabetes, but new research has found that when you exercise can make a big difference.
The study, which was published in the journal Diabetes Care, followed 2,416 people with type 2 diabetes who participated in the Look AHEAD study, which is a randomised clinical trial that was designed to examine the long-term effects of lifestyle interventions in people with type 2 diabetes who have overweight or obesity. For the study, participants wore a recording device on their waist to measure their physical activity.
The researchers found that people who did moderate-to-vigorous physical activity in the afternoon had the greatest reduction in blood glucose levels (aka blood sugar) during the first year. It was pretty significant; afternoon exercisers had a drop in blood sugar levels that were 30% to 50% lower than those of other groups.
The researchers also looked at data from the fourth year of the study and found that the afternoon exercise group had maintained that reduction in blood glucose levels. They also had the highest chances of stopping their glucose-lowering medications.
Elevated blood sugar levels can put people with type 2 diabetes at risk for serious complications of the disease, including heart disease, vision issues and kidney disease, according to Diabetes Australia.
“We have known for a while in people with type 2 diabetes that physical activity is important to help manage blood sugar,” says study co-author Dr Roeland J.W. Middelbeek. “A lot of studies have looked at how much people should do it, but there had not yet been detail on when to do it. This is recognition that the body’s response to handling blood sugar is different during different times of day.”
But why might exercise in the afternoon help with blood sugar management? Here’s the deal.
How does exercise influence blood sugar?
At baseline, any form of exercise is known to help lower blood sugar, explains Dr Middelbeek, and there are a few different ways this can happen.
Exercise increases your sensitivity to insulin, a hormone that helps blood sugar enter the body’s cells so it can be used for energy, the American Diabetes Assocation (ADA) says. That helps your muscle cells better use any available insulin to take up glucose during and after you work out.
When your muscles contract during physical activity, it also helps your cells take up glucose and use it for energy, whether insulin is available or not, the ADA notes. Over time, this can help lower your blood sugar levels and make insulin in your body work more efficiently, Dr Middelbeek says.
Working out regularly also helps build lean muscle mass, and that can help raise your metabolism, which can also help indirectly lower blood sugar, says personal trainer and nutritionist Albert Matheny.
Regular exercise also has lasting benefits for blood sugar management. “Long-term, it also helps to improve the body’s sensitivity to insulin which is beneficial to metabolic health as it helps to maintain stable blood sugar levels,” says endocrinologist Dr Christoph Buettner.
Why can exercise in the afternoon help with blood sugar management?
It’s important to point out that the study didn’t prove that exercising in the afternoon causes reductions in blood sugar, it just found a link. But there are some theories on what could be behind this.
It “makes sense” that the timing of your workout can impact your blood sugar levels, Matheny says. “Blood sugar increases after you eat.”
But blood sugar is usually higher in the afternoon because you’ve likely already eaten breakfast, lunch, and maybe even a snack, he says. “Working out at that point will help lower or manage your blood sugar,” he says.
Dr Middelbeek agrees. “If you’ve eaten, blood sugar generally rises and exercise can help bring that down,” he says.
Your body’s sensitivity to insulin may also run higher during the afternoon Dr. Buettner says. “Insulin sensitivity tends to be higher in the afternoon compared to the morning which may enhance the metabolic benefits of exercise,” he says. “It will also result in lower glucose and lipid levels in the bloodstream in the evening, which will last throughout the night and that likely is beneficial.”
Don't leave it too late in the day though; working out too close to bedtime could mess with your sleep, according to another recent study.
What happens if you can’t exercise in the afternoon?
Dr Middelbeek says that people with type 2 diabetes should look at exercise as part of their treatment plan, along with eating a healthy diet and taking glucose-lowering medications, if they’re recommended by a doctor.
“We recommend that people become active and stay active to the extent that they can,” he says. “The more people can stay active, the better it is for their overall health.” Dr Buettner just recommends that people with type 2 diabetes be prepared for too-low blood sugar levels during or after exercise, especially if they are on supplemental insulin or blood glucose-lowering drugs.
“Exercise can sometimes cause blood sugar levels to drop too low (hypoglycaemia),” he says. “Carry a source of fast-acting carbohydrates, such as glucose tablets or a small snack, in case you experience hypoglycaemia during or after exercise.”
If you can’t exercise in the afternoon, Dr Middelbeek recommends just making sure you get exercise, period.
“A lot of us who study this will still say that any time you can exercise is good,” he says. “We know a lot of people are not active in the afternoon. Whenever people can be active is great. But the afternoon may be slightly better for glucose management.”
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