01 Nov Study Finds Insulin Resistance Improved with Afternoon or Evening Exercise
MedicalResearch.com Interview with:
Jeroen van der Velde, PhD
Leiden University Medical Center
Dept. Clinical Epidemiology, C7-102
Leiden, The Netherlands
MedicalResearch.com: What is the background for this study?
Response: We hypothesized that, in addition to the amount of physical activity, the pattern in which physical activity is accumulated over the day is relevant for metabolic health.
Several studies previously showed beneficial effects of interrupting sedentary periods with short periods of activity (breaks in sedentary time) on glucose control. In addition, very recently it has been argued that the timing of physical activity during the day may be relevant for metabolic health. This was mainly shown in animal studies and intervention studies with supervised high intensity exercise training in men with impaired glucose control or type 2 diabetes. If timing of physical activity matters in a ‘free-living’ setting in the general population is largely unknown.
Therefore, our aim was to investigate associations of timing of physical activity and breaks in sedentary time with liver fat content and insulin resistance in a middle-aged population.
MedicalResearch.com: What are the main findings? Did the type of exercise matter?
Response: We did not observe associations of number of breaks in sitting time with reduced liver fat or insulin resistance. However, higher total physical activity energy expenditure (PAEE) and, particularly, more moderate-to-vigorous physical activity (MVPA) was associated with reduced liver fat and insulin resistance. Interestingly, we observed that the timing of MVPA during the day was associated with insulin resistance: MVPA in the afternoon or evening but not in the morning was associated with reduced insulin resistance compared with having an even distribution of MVPA during the day.
In our study, we mainly focused on MVPA as determined from combined heart rate and accelerometer data. Activities are often reported using a MET value; the Metabolic Equivalent of Task, where a MET value of 1 equals energy expenditure in rest. MVPA are all activities with a MET-value>3, thus with an energy expenditure of at least 3-times resting energy expenditure. These activities would include most sport activities, but also brisk walking and cycling (note that this latter activity is very common in the Netherlands). However, we do not know the actual activity our participants were engaging in, only the intensity of all their activities throughout the day.
MedicalResearch.com: What should readers take away from your report?
Response: The time of day when you are mostly active, may be important for optimal effects on glucose control.
MedicalResearch.com: What recommendations do you have for future research as a results of this study?
Response: We are just starting to comprehend to potential health benefits of timing of physical activity. In our study we have looked at difference on a group level and in order to translate our findings into e.g. an intervention, there are several things we need to understand:
– It is likely that a person’s chronotype is relevant in for the effects of timing of physical activity. For instance, does physical activity at a certain time during the day affect people that can be considered ‘morning persons’ and ‘evening persons’ in a similar way?
– Who can benefit from timed physical activity? Everyone, people living with obesity, people living with type 2 diabetes?
– Will adapting your timing of physical activity indeed lead to improvements in glucose control? Our study is a cross-sectional study, so causal inferences (does timing of physical activity cause a change in glucose control) should be done with caution. Thus, it would be very interesting to perform an intervention study in which the timing of physical activity is changed (but the total amount of activity remains similar) and to measure if e.g. glucose levels improve in a population of persons at risk for type 2 diabetes.
– Timing of physical activity is only a piece of the puzzle. Timing of other lifestyle behaviors such as sleep and food intake are important cues for our circadian system as well and it is likely that metabolic responses are the result of an interaction between all these behaviors.
MedicalResearch.com: Is there anything else you would like to add? Any disclosures?
Response: We are currently involved in a large research consortium with several research institutes in the Netherlands and Canada: TIMED (“The right timing to prevent type 2 Diabetes”) to find answers to the abovementioned questions.
We have no relevant disclosures for this work.
van der Velde, J.H.P.M., Boone, S.C., Winters-van Eekelen, E. et al. Timing of physical activity in relation to liver fat content and insulin resistance. Diabetologia (2022). https://doi.org/10.1007/s00125-022-05813-3
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