A recent study published in Portliness investigates differences in the timing of moderate-to-vigorous physical activity (MVPA) and its impact on blood glucose levels and metabolic function in sedentary overweight and obese adults.
Study: Effect of timing of moderate-to-vigorous lifestyle physical activity on glycemic control in sedentary adults with overweight/obese and metabolic disorders. Image credit: Nomad_soul / Shutterstock.com
How does time of day affect glucose levels?
Obese individuals are more likely to develop impaired glucose tolerance, insulin resistance, and type 2 diabetes mellitus. Weight reduction through dietary management and physical activity (PA) is often recommended to improve glycemic control in obese individuals.
MVPA is effective in glucose homeostasis among subjects who are obese or overweight. However, the optimal timing of MVPA remains unclear.
Physiological processes are regulated by circadian rhythms. Therefore, blood glucose levels fluctuate throughout the day. Skeletal muscle is primarily responsible for removing glucose from the blood, and reduced uptake by muscle cells in the afternoon and evening contributes to elevated blood sugar levels during these hours.
Thus, MVPA later in the day could improve glucose homeostasis. This has been shown in previous studies looking at nocturnal glucose and glycated hemoglobin (HbA1c) levels.
Previous studies have often focused on lifestyle physical activity (PA) in association with nocturnal and diurnal glucose levels, mainly during fasting and without considering time. This was the motivation for the current study, in which MVPA time as part of daily life was assessed in relation to glucose levels.
What did the study show?
The current study included 186 adults with a mean age of 46.8 years. Both men and women were equally represented. All study participants were either obese or overweight, with an average body mass index (BMI) of 32.9.
The 14-day study period was classified as inactive days or days when participants were somewhat active, active, or very active based on World Health Organization (WHO) guidelines for physical activity. Activity was monitored using accelerometers, while glucose levels were recorded by continuous glucose monitors.
Activity time was recorded as morning, afternoon, or evening PA, which reflected activity performed between 6:00 A.M. and 12:00 p.m., 12:00-6:00 p.m. and 6:00 p.m. to 12:00 am respectively. Mixed MVPA reflected PA without clear timing.
Mixed MVPA accounted for more PA than any other timing group. Average MVPA was 24 minutes per day.
Some activity was associated with lower blood glucose levels, including 24-hour, daytime or nighttime compared to being inactive. Specifically, mean 24-hour glucose levels were 1.0 and 1.5 mg/dL lower on somewhat and very active days, respectively, compared to inactive days. Similarly, nocturnal glucose levels decreased by 1.5, 1.6, and 1.7 mg/dL on somewhat active, active, and very active days, respectively.
Lower daytime, nighttime, and 24-hour blood glucose levels were reduced when MVPA was performed more frequently between 6 p.m. and midnight. Morning and mixed MVPA patterns were not associated with changes in blood glucose levels.
Both 24-hour and nocturnal blood glucose levels were lower with the evening exercise compared to the inactive group. Overall, increased daily MVPA was associated with lower 24-h and nocturnal glucose levels.
These improvements were particularly notable among both male and female participants with impaired glucose regulation. Additionally, 150-300 minutes of MVPA each week results in improved blood glucose control compared to inactivity.
These findings highlight the promising area of MVPA timing as a novel approach to improve metabolic health in individuals at risk of developing cardiovascular disease.”
conclusions
Study findings suggest that accumulation of MVPA primarily during the evening hours is associated with better stabilization of blood glucose levels among obese and overweight sedentary adults with reduced metabolism. Thus, both the optimal volume and timing of daily activity are critical to maintaining glucose control.
These findings are consistent with previous studies that observed reduced insulin resistance among adults with a high BMI who were more active in the afternoon or evening compared to mixed or morning activity.
Mechanisms responsible for this association may include an increase in the efficiency of glucose uptake in skeletal muscle during a period when it is low, along with insulin sensitivity. In addition, nocturnal RA may upregulate circadian genes in skeletal muscle that are key to metabolic processes. Exercise can also increase translocation of glucose transporter type 4 (GLUT-4).
Even among people with diabetes, evening exercise may enhance glycemic control compared with morning exercise, which increases cortisol levels and subsequently causes hyperglycemia. In more active individuals, the observed effects could be greater.
Future research is needed to investigate these patterns in older adults and diabetic individuals, who have the greatest need for euglycemic interventions.
Journal Reference:
- Clavero-Jimeno, A., Dote-Montero, M., Migueles, JH, et al. (2024). Effect of timing of moderate-to-vigorous lifestyle physical activity on glycemic control in sedentary adults with overweight/obese and metabolic disorders. Portliness. doi:10.1002/oby.24063.
