Afternoon exercise is more efficacious than morning exercise at improving blood glucose levels in individuals with type 2 diabetes: a randomised crossover trial.
Level 2 - randomized trial
Individual randomized crossover trial in humans
PubMed 30426166 · doi:10.1007/s00125-018-4767-z
What was done
Eleven men with type 2 diabetes (aged 45–68 years, BMI 23–33 kg/m², non-insulin-treated, without other systemic illness) participated in an unblinded randomized crossover trial. Participants completed 2 weeks of high-intensity interval training (HIIT) 3 sessions per week in either the morning or afternoon, followed by a 2-week washout period, and then 2 weeks of the opposite timing regimen. Continuous glucose monitoring (CGM) and serum TSH and T4 concentrations were measured.
What was found
Morning HIIT increased CGM glucose on exercise days in week 1 to 6.9 ± 0.4 mmol/l (mean ± SEM) compared with pre-training (6.4 ± 0.3 mmol/l) and afternoon HIIT (6.2 ± 0.3 mmol/l). Afternoon HIIT decreased CGM glucose compared with pre-training and morning HIIT. Afternoon HIIT was associated with higher TSH (1.9 ± 0.2 mU/l vs 1.4 ± 0.2 mU/l pre-training) and lower T4 (15.8 ± 0.7 pmol/l vs 16.8 ± 0.6 pmol/l pre-training). Morning HIIT increased TSH (1.7 ± 0.2 mU/l) with no change in T4.
Why it matters
These findings suggest that exercise timing modulates glycemic responses in type 2 diabetes, with afternoon sessions yielding superior glucose-lowering effects compared to morning sessions.
Limits
The sample size was very small (n = 11) and limited strictly to men not taking insulin. The intervention lasted only 2 weeks per arm, researchers were not blinded, and long-term durability of these glycemic effects was not evaluated.
Cited by
- supports A Stockholm study found that high-intensity interval training in the morning raised blood glucose in individuals with diabetes, while the same exercise in the late afternoon lowered 24-hour blood glucose.