Inflammatory markers and blood glucose are higher after morning vs afternoon exercise in type 2 diabetes.

AIMS/HYPOTHESIS: The aim of this study was to investigate effects of time of day on glucose management in individuals with type 2 diabetes undertaking high-intensity interval exercise. Additionally, the association between regular eating behaviour and mean amplitude of glycaemic excursions was examined. Specifically, the primary outcome was to determine the effect of the intervention on 24 h glucose levels.

METHODS

A crossover trial was conducted, comprising 12 men and 12 women with type 2 diabetes and 12 men and 12 women without diabetes. Participants performed high-intensity interval exercise sessions in the morning (09:00 hours) or afternoon (16:00 hours) on separate days at least 7 days apart. Standardised meals were provided the day before exercise, on the day of exercise and on the day after exercise. Continuous glucose monitoring was used to estimate blood glucose levels.

RESULTS

The 24 h glucose profile did not differ between morning and afternoon exercise across cohorts. However, morning exercise increased blood glucose during the 2 h post-exercise period in men (p<0.05) and women (p<0.01) with type 2 diabetes, but blood glucose was unaltered following afternoon exercise. Glycaemic variability (assessed using the mean amplitude of glycaemic excursions) was reduced during the 3 day meal intervention in men (p<0.001) and women (p<0.05) with type 2 diabetes, but not in individuals without diabetes. Participants exhibited higher morning cortisol levels (p<0.001) compared with afternoon cortisol levels, independently of diagnosis. Individuals with type 2 diabetes exhibited higher levels of the inflammation marker C-reactive protein (p<0.001) and the heart failure marker NT-proBNP (p<0.001) in the morning than in the afternoon.

CONCLUSIONS/INTERPRETATION: In type 2 diabetes, afternoon high-intensity interval exercise appears to be more effective than morning high-intensity interval exercise for maintaining glucose management. Further research is needed to explore how elevated morning cortisol levels and inflammatory markers influence the exercise response and affect glucose regulation. Additionally, consistent meal timing and controlled energy intake are recommended for reducing the mean amplitude of glycaemic excursions.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05115682.