Performing moderate-to-vigorous activity (MVPA) in the afternoon or evening may improve blood glucose control to a greater extent than exercising evenly throughout the day, new research suggests.
The data comes from 775 participants with a mean body mass index (BMI) of 26.2 kg/mtwo in the Dutch Observational Epidemiology of Obesity (NEO) study. The use of activity monitors for four consecutive days showed that MVPA performance (defined as activity with an intensity of > 3 metabolic equivalents of task) in the afternoon or evening was associated with a reduction of up to 25% insulin resistance compared to a uniform distribution of activity throughout the day.
“This is one of the first studies in humans where the relationship between the timing of physical activity and insulin resistance was examined,” said lead author Jeroen van der Velde, from the Department of Clinical Epidemiology, Leiden University Medical Center, the Netherlands. Medscape Medical News.
In addition, he noted that while previous interventional studies have shown a greater reduction in blood glucose with high-intensity exercise performed in the afternoon compared to the morning in people with impaired glucose metabolism or type 2 diabetes“To my knowledge, we were the first to use a population-based study in a general population to study this.”
Katarina Kos, MD, PhD, Senior Lecturer in Diabetes and Obesity at the University of Exeter, UK, said, “This study is novel because it links the timing of physical activity whether it is done in the morning, afternoon or evening with insulin resistance and fat content.This is from a cohort of middle-aged Dutch people between the ages of 45 to 65 studied 10 years ago and based on self-reported weight and eating behavior and found to be overweight at general”.
Does it come down to circadian rhythm?
“The results are interesting because whether the chosen time was in the afternoon (63% of the study population) or at night (8% of the study population), it seemed to be associated with an improved metabolism compared to morning exercise … (16% of the population). Whether this was due to the (timing) of the activity has yet to be shown,” he told the UK’s Science Media Centre.
van der Velde agrees that the effect can be explained, at least in part, by the body’s circadian rhythm. “Physical activity can act as… a signal for the activation of clock genes. Previous research has suggested that our body’s muscular system and oxidative system are also affected by our circadian rhythm and their peak activity appears to be in the late afternoon. So, being most active in this time frame … may elicit greater metabolic responses compared to being active in the morning.”
But, he cautioned, “I think it’s important to realize that we’re just beginning to understand the potential impact of timing of physical activity. At this stage, I think it’s more important to be physically active in general. So … if the morning it’s the only time of day to go for a walk or a run, certainly do this.”
Kos agreed: “As this is not an interventional study, more research is needed to explain the cause of the observed association.”
van der Velde also added that it is not yet clear which individuals or subgroups might experience additional benefits from timed activities. That is the current research focus of a large consortium from various research institutes in the Netherlands and Canada.
Timed exercise reduces insulin resistance, but not liver fat
The findings were Posted online November 1 at diabetology.
The study population included men and women living in the Leiden metropolitan area in the west of the Netherlands, who were between 45 and 65 years old and who reported a BMI of 27 kg/mtwo or higher. A second cohort included inhabitants of a municipality who were invited to participate regardless of their BMI. All wore the activity monitors for 4 consecutive days and nights during their usual activities.
Neither sedentary time nor breaks in sedentary time (defined as a period of activity with acceleration > 0.75 m/s)two after a sedentary period) were associated with lower insulin resistance, calculated by blood sampling.
However, the number of breaks in sedentary time was associated with significantly higher liver fat content by 22%, as assessed by proton magnetic resonance spectroscopy.
One reason for the lack of effect of pauses on insulin resistance, the authors theorize, is that this was a real-world observational study in which regular pauses are not common. Alternatively, people may not have been intensely active enough during breaks to make a difference.
After adjustment for total body fat, an additional hour of MVPA was associated with a 5% drop in insulin resistance. An additional hour of MVPA in 5-minute shifts was associated with 9% less insulin resistance.
Furthermore, after adjustments, insulin resistance was significantly reduced in participants who were more active in the afternoon, by 18%, or at night, by 25%, while insulin resistance was not was affected among those who were most active in the morning (–3%). , all compared to people who spread their MVPA throughout the day.
Timing of MVPA was not associated with liver fat content, and there were no significant differences in liver fat content and insulin resistance between groups based on timing of light physical activity.
“This is just speculation, but perhaps the circadian system is less involved in fat accumulation in the liver. Or perhaps the timing of other lifestyle variables is more important here, such as dietary intake,” van said. der Velde.
Finally, he observed: “It is very likely that the timing of physical activity is just one piece of the puzzle. The timing of other lifestyle behaviors, such as sleep and food intake, are also important cues for our circadian system, And it’s likely that all of these behaviors interact with each other.”
The NEO study is supported by the Leiden University Medical Center, the Netherlands Cardiovascular Research Initiative, an initiative supported by the Dutch Heart Foundation and the Netherlands Organization for Health Research and Development/Partnership Diabetes/Dutch Diabetes Foundation Breakthrough. van der Velde has reported no further revelations.
Diabetology. Posted online November 1, 2022. Text complete
Miriam E. Tucker is a freelance journalist based in the Washington, DC area. She is a regular contributor to Medscape, and her other work appears in The Washington Post, NPR’s Shots blog, and Diabetes Forecast magazine. She is on Twitter: @MiriamETucker.
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