Diabetologia: The best time to exercise for a significant improvement of 25% insulin resistance is...

The current obesity pandemic is partly the result of
physical inactivity and sedentary (sedentary) during the day.
Sedentary behavior is associated
with an increased risk of cardiometabolic diseases, including type 2 diabetes.
Some studies have shown that short breaks for sedentary periods are associated with improvements in cardiometabolic conditions, with prolonged sitting or frequent interruptions in light activity improving blood sugar responses and triacylglycerol levels
.

Previous studies have shown that exercise is associated with lower liver fat content, which improves insulin sensitivity
.
Therefore, this study hypothesizes that disruption of sedentary time may reduce liver fat and insulin resistance, ultimately preventing type 2 diabetes
.

In addition to the duration of inactivity, it has been suggested that the time spent physically active during the day may be related to
metabolic health.
However, only a few studies examined the association between all-day activity time and metabolic risk markers in humans, and the results were inconsistent
.
In the general population, the importance of physical activity time in relation to metabolic health is currently unclear
.

Therefore, this study aimed to explore the association
between physical activity and sedentary rest and liver fat content and insulin resistance in middle-aged people.

In the Dutch Obesity Epidemiology (NEO) study, the researchers used activity sensors to assess sedentary time, sedentary time and physical activity of varying intensity, and assessed liver fat content by magnetic resonance (n = 256).

Participants were categorized as most active in the morning (06:00-12:00), afternoon (12:00-18:00), or evening (18:00-00:00), as well as moderate to vigorous physical activity (MVPA)
evenly distributed throughout the day.
Being most active in a certain period of time is defined as the total daily MVPA
that spends most of (%) during that time period.

Using linear regression analysis, the researchers looked at the relationship between sedentary time, rest time, and MVPA time on the liver fat content and HOMA-IR, and adjusted for
demographic and lifestyle factors, including body fat.

The results showed that the mean (SD) age of the participants (42% of men) was 56 (4) years and the mean (SD) BMI was 26.
2 (4.
1) kg/m²
.
Total sedentary time was not associated with liver fat content or insulin resistance, while rest time during sedentary time was associated
with higher liver fat content.
Total MVPA (-5%/h [95% CI -10%/h, 0%/h]) and duration of MVPA were associated with reduced insulin resistance but not
liver fat content.

Compared with participants with evenly distributed MVPA throughout the day, insulin resistance was similar in the most active participants in the morning (-3% [95% CI -25%, 16%]), while insulin resistance was reduced
in the most active participants in the afternoon (-18% [95% CI -33%, -2%]) or evening (-25% [95% CI -49%, -4%]).

The number of daily breaks for sedentary times was not
associated with lower liver fat content or reduced insulin resistance.
Moderate to strenuous activity in the afternoon or evening is associated with
a reduction in insulin resistance of up to 25%.
Further research should assess whether the timing of physical activity is also important
for the development of type 2 diabetes.

Original source:

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