A study recently published obesity This study explores differences in time of moderate-to-vigorous physical activity (MVPA) and its effects on blood glucose levels and metabolic function in overweight and obese inactive adults.
Study: Effect of lifestyle moderate-to-vigorous physical activity time on glycemic control in sedentary adults with overweight/obesity and metabolic disorders. Image credit: Nomad_soul / Shutterstock.com
How does the time of day affect glucose levels?
Obese people are more likely to have impaired glucose tolerance, insulin resistance, and type 2 diabetes. Weight loss through dietary management and physical activity (PA) is often recommended to improve glycemic control in obese individuals.
MVPA is effective in improving glucose homeostasis in obese or overweight individuals. However, the optimal timing of MVPA is still unclear.
Physiological processes are regulated by circadian rhythms; therefore, blood glucose levels fluctuate throughout the day. Skeletal muscles are primarily responsible for clearing glucose from the blood, while lower absorption by muscle cells during the afternoon and evening contributes to increased blood glucose levels at these times.
Thus, MVPA may improve glucose homeostasis at the end of the day. This has been demonstrated in previous studies examining nighttime glucose and glycated hemoglobin (HbA1c) levels.
Previous studies have often focused on the association of lifestyle physical activity (PA) with nighttime and daily glucose levels, mostly during the fasting state and regardless of the time. This motivated the current study, in which the timing of MVPA as part of daily life was assessed against glucose levels.
What did the study reveal?
The current study included 186 adults with an average age of 46.8 years. There was equal representation of both men and women. All participants in the study were either obese or overweight, with an average body mass index (BMI) of 32.9.
The 14-day study period was categorised into inactive days or days in which participants were somewhat active, active or very active based on the World Health Organisation (WHO) guidelines on physical activity. Activity was monitored using accelerometers, while glucose levels were recorded by continuous glucose monitoring devices.
Activity time was recorded as morning, afternoon, or evening PA, reflecting activity performed between 6:00 a.m. and 12:00 p.m., 12:00-6:00 p.m., and 6:00 p.m. and 12:00 a.m., respectively. Mixed MVPA reflected PA without a clear time.
Mixed MVPA involved more PA than any other timing group. The average MVPA was 24 minutes per day.
Some activity was associated with lower blood sugar levels over 24 hours, including diurnal or nightly, compared with being inactive. More specifically, compared with inactive days, 24-hour average glucose levels were 1.0 and 1.5 mg/dL lower during somewhat and very active days, respectively. Similarly, nighttime glucose levels were reduced by 1.5, 1.6 and 1.7 mg/dL on somewhat active, active and very active days, respectively.
More frequent MVPA between 6 p.m. and midnight was associated with decreased daily, nighttime, and 24-hour blood sugar levels. Morning and mixed MVPA patterns were not associated with any changes in blood sugar levels.
Those with evening exercise had the lowest 24-hour and nighttime blood sugar levels compared with the inactive group. Overall, increases in daily MVPA were associated with reductions in 24-hour and nighttime glucose levels.
These improvements were particularly notable in male and female participants with impaired glucose regulation. Furthermore, 150–300 minutes of MVPA per week resulted in better blood glucose control compared with inactivity.
These findings highlight the promising area of MVPA time as a new approach to improve metabolic health in people at risk of developing cardiovascular disease,
conclusion
The study findings suggest that accumulation of MVPA in the evening is associated with better stabilization of blood glucose levels in obese and overweight inactive adults with impaired metabolism. Thus, both the optimal amount and timing of daily activity are important for maintaining glucose control.
These findings agree with earlier studies that found reduced insulin resistance in adults with higher BMIs who were most active in the afternoon or evening, compared with mixed or morning activity.
Mechanisms responsible for this relationship may include increased efficiency of glucose uptake into skeletal muscle when exercise is performed as well as decreased insulin sensitivity. In addition, nighttime physical activity may upregulate circadian genes in skeletal muscle that are important for metabolic processes. Exercise may also increase the translocation of the glucose transporter type 4 (GLUT-4).
Even in individuals with diabetes, evening exercise may improve glycemic control compared with morning exercise, which increases cortisol levels and consequently induces hyperglycemia. In more active people, the effects observed may be greater.
Future research is needed to explore these patterns in the elderly and patients with diabetes, as they are most in need of euglycemic interventions.
Journal Reference:
- Clavero-Gimeno, A., Dote-Montero, M., Miguels, JH, and others. (2024). Effect of timing of lifestyle moderate-to-vigorous physical activity on glycemic control in sedentary adults with overweight/obesity and metabolic deficiencies. obesity. doi:10.1002/oby.24063.