A new study published in Diabetologia (the journal of the European Association for the Study of Diabetes [EASD]) finds that physical activity in the afternoon or evening is associated with lower insulin resistance (and therefore , better blood sugar control) compared to an even distribution of physical activity throughout the day. Morning physical activity offered no benefits, concluded the study by Dr. Jeroen van der Velde and colleagues from the Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands.
The current global obesity pandemic is partly the result of a lack of physical activity combined with sedentary behavior (sitting) during the day. Such behavior is linked to an increased risk of developing metabolic diseases, including type 2 diabetes (T2D), while previous research has found that short breaks in sedentary behavior are associated with an improved cardiometabolic profile. This evidence is supported by experimental studies showing that frequent interruptions of prolonged sitting with standing or light physical activity resulted in lower triacylglycerol levels and a reduction in blood glucose, indicating better blood sugar profile.
High fasting serum triacylglycerol levels may be related to higher liver fat concentrations, which in turn is strongly associated with insulin resistance. Previous studies have shown that exercise is linked to reducing liver fat and improving insulin sensitivity. The authors hypothesized that taking breaks from sedentary behavior may reduce liver fat, resulting in decreased insulin resistance and ultimately prevention of T2D.
In addition to the importance of the duration of sedentary periods , it has been argued that the timing of physical activity throughout the day may be a factor in metabolic health. In vitro studies and animal research have revealed day-dependent changes in exercise capacity as well as associated metabolic risk markers; However, little research of this type has been conducted in humans and its results are inconsistent. Therefore, the team set out to investigate the associations between the timing of physical activity and breaks in sedentary time with liver fat content and insulin resistance in a middle-aged population.
The researchers used data from the Netherlands Epidemiology of Obesity (NEO) study, a prospective population-based cohort study designed to investigate the processes involved in the development of obesity-related diseases. Study participants were recruited between 2008 and 2012, and men and women living in the Leiden metropolitan area were invited to participate if they were between 45 and 65 years old and had a self-reported body mass index (BMI) of 27 kg/m2. or more. Invitations were also sent to all inhabitants of a municipality in the region aged between 45 and 65 years, as a reference population with a BMI representative of the general Dutch population, resulting in a study population of 6,671. people.
Participants underwent a physical examination during which blood samples were taken to measure fasting and postprandial (after meal) blood glucose and insulin levels, while demographic, lifestyle, and clinical information was collected. obtained through a questionnaire. They were also assessed for suitability for an MRI, and approximately 35% of those able to undergo the procedure were randomly selected to have their liver fat content measured using this technique.
Another random subsample of 955 participants were given a combined accelerometer and heart rate monitor to wear for four consecutive days and nights to monitor movement and activity. Measurements of acceleration and heart rate were used to estimate physical activity energy expenditure (PAEE, measured in kJ/kg/day), which in turn allowed the team to determine time spent at different activity intensities. These were expressed as metabolic equivalents of task (MET), a ratio of PAEE during an activity relative to rest (and a standard method for measuring physical activity).
Sedentary periods ( excluding sleep) were defined as ≤1.5 MET, while a break in sedentary time was indicated by a period of activity with accelerations >0.75 m/s2 (as such accelerations have been established by previous research as an accurate indicator of break) to sedentary time). An intensity of more than 1.5 METs up to 3 METs was defined as light physical activity (LPA), with even higher intensities classified as MVPA.
The day was divided into three blocks: morning (06:00-12:00); afternoon (12:00-18:00); and in the afternoon (18:00-24:00), with the proportion of total daily MVPA occurring in each of which reveals the most active period. If MVPA participation in each block differed from the others by less than 5%, then it was classified as an even distribution of activity across the day.
This study is based on the analysis of the results obtained from those 775 participants for whom complete data sets were available. The group was 42% male and 58% female, had an average age of 56 years and an average BMI of 26.2 kg/m2. After adjusting for variables such as age, sex, ethnicity, and total body fat, the researchers observed that higher total PAEE, and in particular MVPA, were associated with both reduced liver fat content and lower reduced insulin resistance .
An association was also found between insulin resistance and the timing of MVPA during the day: performing MVPA in the afternoon or evening was associated with a reduction in insulin resistance, by 18% and 25%. % respectively, compared to a uniform distribution of activity throughout the day. even after adjustment for the full amount of MVPA. There was no significant difference in insulin resistance between morning activity and activity spread evenly throughout the day.
Neither the amount of sedentary time nor the number of interruptions in sedentary behavior was found to have a favorable association with liver fat content or insulin resistance. The authors suggest: “It could be that in our study the intensity of activity during breaks was too light to cause metabolic responses. "Most daily activities are of light intensity and because we did not observe an association between LPA and insulin resistance, this may also explain the lack of association between breaks and insulin resistance."
The timing of physical activity is a relatively unexplored field in human biology and the mechanisms underlying the potential benefits of physical activity timing remain unclear. Previous studies have shown that metabolic responses to high-intensity exercise differ depending on the time of day the exercise was performed. Furthermore, muscle strength, as well as the metabolic function of skeletal muscle cells, show a peak in the late afternoon, suggesting that being more active during this period may result in a more pronounced metabolic response than activity performed later. early in the day.
The researchers conclude that "in addition to the total amount of daily MVPA, the timing of MVPA during the day was associated with less insulin resistance: performing the majority of MVPA in the afternoon or evening was associated with up to 25% less insulin resistance compared to an even distribution of MVPA throughout the day. These results suggest that the timing of physical activity throughout the day is relevant to the beneficial effects of physical activity on insulin sensitivity. "Inulin. Further studies should evaluate whether the timing of physical activity is really important for the development of type 2 diabetes."
Conclusions/interpretation
|
