How Exercise Timing Affects Your Blood Sugar

New research shows that when you work out might have a significant effect on your blood sugar levels, even health ramifications.

By Elizabeth Millard |

  • A new study published in the journal Diabetologia suggests that when you exercise can play a significant role in blood sugar management.
  • Participants who worked out in the afternoon and evening had 18 and 25 percent reductions in insulin resistance, respectively. Morning exercisers saw no reduction.
  • Keep in mind that any exercise—no matter what time of day you do it—can help with prediabetes and diabetes management, but talk to your doctor before starting a new routine.

Those with prediabetes and diabetes are often encouraged to exercise, and for good reason. Research has linked more activity with better condition management.

But there’s a caveat: Because exercise makes the body more sensitive to insulin, it can increase the risk of blood sugar dropping too low. This is why the American Diabetes Association recommends checking blood sugar more often before and after working out to understand how your body is responding to exercise.

In addition to that strategy, new research published in Diabetologia suggests that the time of day you work out may be another significant factor in better blood sugar control.

Researchers looked at 775 men and women aged 45 to 65 years old, who were given a fitness tracker and placed into one three groups for exercise timing: morning, afternoon, and evening.

They found no changes to insulin resistance—which happens when your body doesn’t respond as it should to insulin, the hormone that regulates blood sugar—for morning exercisers, but improvements in the other two groups. Those who performance moderate to vigorous physical activity in the afternoon had 18 percent lower insulin resistance and the evening group fared even better, with a 25 percent reduction in insulin resistance.

“Our results suggest that in the first place, it’s important to be physically active, and in addition, the time of day may be of further importance for optimal metabolic health,” the study’s lead author, Jeroen van der Velde, Ph.D., researcher at Leiden University Medical Center in the Netherlands, told Bicycling.

These results fall in line with previous research, he added, which showed the most beneficial effects on glucose control with high-intensity exercise training was in the afternoon versus the morning. What was surprising was the large difference between morning and evening, he said.

“We believe this may be explained, at least in part, by the circadian system of our body,” said van der Velde. “Past research suggests our body’s muscular system and oxidative systems are affected by our circadian rhythm, and their peak activity seems to be in the late afternoon. Thus, being mostly active in the afternoon and evening may elicit greater metabolic responses compared to being active in the morning.”

That said, he added that morning exercise is far better than no exercise, and that physical activity is only a piece of the puzzle when it comes to circadian rhythm (and therefore, blood sugar) management—most notably, meal timing and sleep play considerable roles as well.

Another note: Although these findings will apply most directly to those with prediabetes or diabetes, improved blood sugar management is a positive for everyone. According the Centers for Disease Control and Prevention, well-maintained blood sugar is linked to mood regulation, energy levels throughout the day, sleep efficiency, and prevention of serious chronic illnesses like heart disease and kidney disease.

READ MORE ON: blood sugar diabetes training training time workouts

Copyright © 2023 Hearst