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Blood sugar, exercise and timing


ON THE CLOCK Recent studies in Norway and Sweden reveal that afternoon exercise is better than morning exercise for controlling blood glucose levels in people with type 2 diabetes.

The time of your daily exercise might matter more than you think

Andrew O'Brien

There’s no time like the present. Or is there? Obviously that statement depends on an infinite number of variables.
Take swimming for example. If the present is a beautiful sunny day on a beach in the Caribbean, there is clearly no time like it. Alternatively if the present is a wild, windy day on a shark-infested strait, one could argue that there might be a better time.
What about exercise? Is there a good time to exercise?
As we can see from above, context is key, but research might provide some interesting pointers for a particular group of people.
We know that exercise is good for people with type-2 diabetes, assisting in controlling blood sugar levels and weight loss, among other things. But a 2019 study from researchers in Sweden that looked at whether the timing of the exercise was important produced some interesting results.
In the study, eleven men with type-2 diabetes who were not on insulin treatment completed two weeks of high-intensity interval training, either in the morning or the afternoon. Then, after a two-week break, the timing of their sessions was switched. The researchers found that while the afternoon exercise sessions lowered blood glucose, morning sessions actually had a negative effect, raising blood glucose levels.
A second paper published late last year by researchers in the Netherlands, showed similar findings for moderate-intensity exercise. In this study, men at risk of type-2 diabetes followed a 12-week programme that included three 30-minute sessions on an exercise bike and one resistance-training session each week. Some of the subjects did all of their sessions in the morning, while others attended in the afternoon.
While there was an improvement for both groups, the data showed that those subjects that exercised in the afternoon had a higher insulin sensitivity than the morning group, resulting in better blood glucose control. As an extra benefit, the afternoon group also lost significantly more body fat than the morning group. At this stage, it hasn’t been established why such variations exist, but it may be that afternoon exercise improves evening and overnight metabolism.
These two studies need to be discussed in context. Both studies included only men who either had, or were at risk of developing, type-2 diabetes – meaning that the findings aren’t necessarily applicable to women or men without metabolic problems.
There are, however, plenty of people for whom the findings are relevant.
According to the Healthy Ireland survey, around 850,000 people over the age of 40 in Ireland either have, or are at risk of developing type-2 diabetes. Research would also suggest that men are two to three times more likely to have diabetes. So, for more than half a million men in Ireland, the findings of these papers are pertinent.
For the men who fit into this group, it may be worth combining the findings of these two papers and the WHO exercise guidelines to help plan your weekly exercise.
The aim for most adults should be at least 150 minutes of moderate-intensity exercise or at least 75 minutes of high-intensity exercise per week, along with two resistance-training sessions.
Given that high-intensity exercise seems to produce blood sugar spikes when done in the morning, those sessions would be best scheduled later in the day. For those whose schedule means they can only exercise in the morning, moderate intensity would appear to be the better way to go; the findings were good, just not as good as later in the day.
Perhaps most important is finding an exercise that you enjoy, and that fits into your day as easily as possible.
Walking, either to work or at break times, is as simple as exercise gets, and with everything that’s going on these days, might be the best option for many of the men in this cohort.
A few simple strength exercises done two afternoons a week can complete the programme.
And if you can at least imagine that you’re on that beach in the Caribbean, that will surely make it all the better.

Andrew O’Brien is a chartered physiotherapist and the owner of Wannarun Physiotherapy and Running Clinic at Westport Leisure Park. He can be contacted on 083 1593200 or at