New research suggests that the timing of exercise may affect metabolism, particularly in people with Type 2 diabetes, although staying consistent with physical activity remains the most important factor.
A common question is whether it is better to exercise in the morning or later in the day. However, experts emphasize that any exercise is better than none at all.
A recent major review published in Trends in Endocrinology and Metabolism found that workout timing can, in some cases, have a meaningful impact on how the body responds to exercise.
The researchers examined multiple earlier studies comparing morning exercise with afternoon and evening workouts. These studies included both healthy individuals and people with Type 2 diabetes—a condition affecting millions worldwide in which the body becomes resistant to insulin, leading to persistently high blood sugar levels.
The research found that many of our cells, hormones, and genes respond differently depending on the time of day we exercise.
The effects were especially notable in people with Type 2 diabetes. For them, exercising later in the day was linked to stronger and longer-lasting improvements in blood sugar control. In contrast, similar workouts done in the morning were sometimes associated with higher blood sugar levels and reduced insulin sensitivity.
“There’s a growing body of evidence suggesting that exercise later in the day may offer additional health benefits,” said Trine Moholdt, an exercise scientist at the Norwegian University of Science and Technology in Trondheim, Norway, who was not involved in the review. However, she noted that any added benefits likely depend on the individual and the type of exercise performed.
Exercise and the body clock
One key idea behind these findings is that exercise acts as a “zeitgeber,” or time cue, for the body’s internal clock. Our bodies operate on a 24-hour circadian rhythm controlled by molecular clocks in nearly every cell, coordinated by a central clock in the brain.
These rhythms are influenced by external signals such as light, meal timing, and physical activity. In response, the body regulates hormones and processes like heart rate, blood pressure, insulin release, energy levels, and body temperature throughout the day.
However, in people with Type 2 diabetes, these rhythms are often disrupted, a condition known as circadian misalignment. This means the body’s internal systems may not function in sync, affecting how metabolism responds to daily activities like exercise.
Morning exercise and blood sugar
In one study reviewed, middle-aged men with Type 2 diabetes followed identical exercise routines either in the morning or afternoon. While the workouts were the same, their effects were different.
Afternoon exercise led to lower blood sugar levels that remained stable for up to 24 hours. Morning workouts, however, were linked to higher blood sugar and poorer insulin sensitivity that persisted for hours afterward.
Other studies showed similar patterns. Overall, researchers found that people with Type 2 diabetes often experience higher post-exercise blood glucose in the morning compared to later in the day, suggesting that the body’s metabolic response varies depending on timing.
The role of the “dawn phenomenon”
One explanation is the “dawn phenomenon,” where blood sugar naturally rises in the early morning hours. This happens because cortisol, a stress hormone, increases upon waking and signals the liver to release stored glucose.
In healthy individuals, insulin helps move this glucose into muscles for energy use. But in Type 2 diabetes, insulin production is reduced and the body is less responsive to it, causing blood sugar to remain elevated.
Morning exercise can further increase cortisol levels and energy demand, leading to even more glucose release. While healthy individuals can easily use this fuel, those with Type 2 diabetes may not absorb it efficiently, causing blood sugar to rise further.
As a result, morning workouts may be less effective for improving glucose control in people with Type 2 diabetes compared to later-day exercise.
Any movement still matters
Despite these differences, experts stress that exercise at any time of day is still highly beneficial. “The most important message remains that exercise at any time is better than no exercise at all,” one of the study’s authors emphasized.
For those who prefer morning workouts, lower-intensity activities like brisk walking may be a better option, as they are less likely to significantly disrupt blood sugar levels.
More research needed
Researchers note that most existing studies are small, short-term, and focused mainly on adult men, leaving questions about how women and older adults may respond differently. Additionally, while this review focused on blood sugar control, other outcomes such as heart health, sleep quality, and longevity may also be influenced by exercise timing.
The bottom line
For people with Type 2 diabetes, exercising later in the day may offer better blood sugar benefits. However, for most people, the key takeaway is simple: the best time to exercise is the time you can stick with consistently.
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