Woman running and exercising at night

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GRANADA, Spain — Does the time of day that you exercise make a difference in your health? A new study by scientists at the University of Granada suggests it just might be, particularly if you’re at risk for diabetes. They’ve uncovered a simple yet powerful secret to improving blood sugar levels in adults, especially those who are overweight or obese: working out at night.

The research, published in Obesity, concludes that squeezing in your moderate-to-vigorous exercise in the evening could be the key to optimizing your body’s ability to regulate glucose. This discovery offers an exciting new approach for managing health through strategic physical activity scheduling.

Methodology: Tracking Activity, Glucose Levels Around The Clock

To unravel the relationship between exercise timing and blood sugar control, researchers recruited 186 sedentary adults who were overweight or obese and had at least one metabolic impairment, such as high blood pressure or elevated cholesterol. For 14 days straight, participants wore both an accelerometer on their wrist to track physical activity and a continuous glucose monitoring device to measure blood sugar levels 24/7.

The researchers then classified each day based on when the majority of moderate-to-vigorous physical activity (MVPA) occurred. If more than 50% of MVPA minutes were logged between 6 a.m. and 12 p.m., it was a “morning” day. “Afternoon” days had the bulk of activity between 12 and 6 p.m., while “evening” days saw most movement between 6 p.m. and 12 a.m. Days with a more even spread were labeled “mixed,” and of course, days with no physical activity at all were considered “inactive.”

By comparing glucose levels across these different day types, both within individual participants and across the whole group, the researchers could paint a detailed picture of how exercise timing influenced blood sugar control from hour to hour and day to day.

Results: Evening Exercise Emerges As Glucose-Lowering Champion

The data revealed a clear winner when it came to optimizing glucose levels: evening exercise. On days when participants clocked the majority of their MVPA minutes between 6 p.m. and midnight, their average glucose over the full 24-hour period was about 1.26 mg/dL lower compared to their inactive days. The benefits were even more pronounced overnight, with mean nocturnal glucose dropping by 2.16 mg/dL.

Impressively, the positive impact of evening exercise on glucose control was consistent in both men and women.

Afternoon exercise also proved beneficial, albeit to a slightly lesser degree. Glucose levels averaged nearly 1 mg/dL lower over 24 hours and 1.72 mg/dL lower nocturnally when the bulk of activity occurred between 12 amd 6 p.m.

In contrast, morning MVPA didn’t produce statistically significant glucose improvements compared to inactive days, suggesting that the perks of physical activity may be amplified later in the day.

Notably, the glucose-lowering effect of evening exercise was most potent in participants who already had impaired glucose regulation, hinting that this strategy could be especially powerful for those at higher risk of developing diabetes.

Discussion & Takeaways: Harnessing Circadian Rhythms For Metabolic Health

It’s clear from the study that not all exercise is created equal when it comes to glucose control. The findings suggest that our bodies may be more primed to benefit from physical activity later in the day, likely due to complex interactions between exercise and our natural circadian rhythms.

Prior research has shown that factors like insulin sensitivity and glucose uptake in muscle tissue tend to be lower in the evening hours. Therefore, engaging in MVPA at this time may provide a more potent stimulus to ramp up these flagging metabolic processes, resulting in better overall glucose control. Evening exercise might also help realign the body’s internal clocks in a way that promotes healthier blood sugar patterns.

While more studies are needed to fully unravel the mechanisms at play and determine if these findings extend to other populations like older adults or people with diabetes, this research provides an exciting jumping-off point for rethinking exercise prescriptions. For folks looking to optimize their metabolic health, aiming for more afternoon and evening activity could be a smart strategy.

But, the researchers caution, the goal isn’t to cram all your exercise into one time slot. Ultimately, the best approach is to stay consistently active and avoid long sedentary stretches. If you can layer on a bit more intentional MVPA in the afternoon or evening hours, however, you might just give your glucose control that extra edge.

“Our results highlight the importance of the field of precision exercise prescription. In clinical practice, certified sports and medical personnel should consider the optimal timing of the day to enhance the effectiveness of the exercise and physical activity programs they prescribe,” says study co-author Dr. Jonatan R. Ruiz, PhD, professor of physical activity and health at the University of Granada, in a statement.

At a time when rates of obesity and diabetes continue to climb, these findings empower us with a new tool to promote metabolic wellbeing. By aligning our workouts with our body’s natural rhythms, we may be able to coax our cells toward better glucose balance and create a foundation for lasting health. As the old adage goes, timing really is everything — and that just might include the timing of your evening run or bike ride.

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