There is a maddening endless quest to tailor your exercise for better heart health, losing belly fat, gaining muscle strength, improving blood sugar control … according to the best time of day for achieving these goals.

Perhaps it’s truer to say that scientists are on a quest to find something new to throw into the already crowded, confusing mix of advice. And publish a new paper about it.

The most recent study comes this week from Harvard – set out to find the best time of day to exercise as a means of preventing type 2 diabetes getting hold of you.

The study

It involved 93,095 UK Biobank participants (mean age 62 years) wearing accelerometers on their wrists for a week.

Some nifty analysis of the accelerometer data allowed the researchers to determine all types of activity undertaken by an individual throughout the day, including chores, walking and vigorous activity.

And what were the results?

The short version: According to a statement from Harvard, being active in the morning or afternoon may be slightly better than being active in the evening when it comes to diabetes prevention.

More helpfully, the study also found that vigorous physical activity was strongly linked to reduced diabetes risk, regardless of the time of day it was done.

A couple of things to think about

Timing is tricky.

Exercising vigorously at night isn’t optimal, because it can lead to broken and unsettled sleep – which is a well-established risk factor for developing type 2 diabetes.

As we prepare for sleep, our body temperature drops, the heart rate slows, and so does our brain waves.

Exercise, however, works the other way – it increases your core body temperature, pushes the heart rate, and you feel wide awake.

This is the scenario if you exercise close to bed time.

But, by exercising a little earlier, what we think of as the evening, when daylight has gone – and you’ve still got a few hours before you hit the hay – exercise is more likely to make you feel relaxed, and could set you up for more restorative sleep.

It may be that the benefits of night exercise (closer to bed time) are cancelled out by even slightly disordered sleep.

Another thing to keep in mind

One of the best ways to ward off type 2 diabetes is going for a light walk after eating.

Why? Because walking for even two to five minutes after a meal significantly slows the rate at which your blood sugar rises and falls.

Regular blood sugar spikes do the damage to your eyes, heart and feet etc.

Want to know more? Read this New York Times report.

And what about previous studies?

When you boil it down, the research has been pretty consistent, particularly experiments with human subjects.

It comes down to this.

If you’re keen to lose more body fat, then do some vigorous exercise between 7am and 9am.

If you have to choose a time of day that is best overall for your health, and your main focus is to reduce your risk of developing type 2 diabetes, then early evening exercise is probably the way to go.

Australian Catholic University researchers in 2021 found that “men who were overweight and at risk of diabetes had better overnight blood sugar control when they exercised in the early evening rather than in the morning”.

The later workouts upped the metabolic health of the evening exercisers more “than those who performed the same exercise earlier in the day”.

A 2022 study from the Netherlands has found exercising in the afternoon or evening has a better impact on insulin resistance “when compared with an even distribution of physical activity through the day”.

In 2021, we reported that intensely exercising in the morning upsets blood sugar regulation, which tends to be more unstable in the morning.