Morning and afternoon physical activity shown to reduce risk of developing type 2 diabetes compared with evening activity

Diabetes, Obesity Metabolism (DOM) NOW—November 2023

Physical activity is an important life-style measure to reduce risks of developing type 2 diabetes. However, the most effective timing, consistency and intensity of physical activity is still not known. To investigate this, a study was undertaken using a cohort of 93 095 UK Biobank participants (mean age 62 years) without a history of type 2 diabetes. All participants wore a wrist-worn accelerometer for 1 week and the investigators converted accelerometer information to estimate metabolic equivalent of task (MET) (a common measure of physical activity), summing MET-hours of total physical activity. MET-hour physical activity captures all types of activity undertaken by an individual throughout the day and is measured with the accelerometer, including chores, walking, and vigorous activity. The investigators measured completed METs within three time segments (morning, afternoon, and evening), divided as 06:00–12:00 h (morning); 12:00–18:00 h (afternoon); and 18:00–24:00 h (evening). Consistency of physical activity was analysed by measuring difference of each person's activity from their own personal average. Those with smaller deviations (variance) were considered to be more consistent. The authors also classed the intensity of exercise to moderate-to-vigorous physical activity (MVPA) and vigorous physical activity (VPA) in association with type 2 diabetes incidence.

Using these analyses, 10% and 9% reduction in risk of type 2 diabetes was seen with morning and afternoon activity, respectively but no statistically significant association was observed between evening physical activity and risk of type 2 diabetes. The reason for this observation is unknown but the investigators speculate that lifestyle factors, such as the amount of sleep and dietary intake, would influence the amount of physical activity in the morning, afternoon, and evening undertaken, and therefore the role activity has in the risk of developing type 2 diabetes. When adjusting for lifestyle factors, the observed associations for MET-hours with different times of day became more precise. Consistency of MET-measured physical activity however was not associated with type 2 diabetes; but intensity was—both MVPA and VPA were associated with decreased risk for type 2 diabetes at all times of the day.

While the study has known limitations—for example, retrospective nature, residual confounding and selected populations, this is the first study to report that the timing of activity may play a role in the mitigation of diabetes risk. In addition, total physical activity but not its consistency over the week is an important factor that influences the risk of developing type 2 diabetes, in other words, individuals who exercise a smaller amount of time more frequently have a similar reduced risk of developing type 2 diabetes as individuals who exercise the same total amount, but with less of a routine. Evidence derived from this study can be utilized in life-style advice for individuals at risk of developing type 2 diabetes. The study was published in the journal Diabetologia.¹