Effects of postprandial exercise on blood glucose levels in adults with type 1 diabetes: a review.
Study Goal
The researchers aimed to evaluate the glycaemic effects of postprandial High-Intensity Interval Training (HIIT) in individuals with type 1 diabetes, focusing on blood glucose changes and hypoglycaemia occurrence.
Results Summary
HIIT caused acute glycaemic declines, with the smallest effect size compared to other exercise modalities. Pre-exercise insulin reductions helped protect against hypoglycaemia, but nocturnal hypoglycaemia remained a risk after higher intensity exercise, which could be mitigated with post-exercise snacks and insulin adjustments.
Population
Adults with type 1 diabetes.
Effective Dosage
Not specified.
Duration
Not specified.
Interactions
Insulin adjustments (reductions) with pre- and post-exercise meals were noted to manage blood glucose levels.
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
walking exercise (WALK) | decrease | blood glucose | adults with type 1 diabetes | - | caused consistent acute glycaemic declines | #1 |
continuous exercise of moderate intensity (CONT MOD) | decrease | blood glucose | adults with type 1 diabetes | - | caused consistent acute glycaemic declines | #2 |
continuous exercise of high intensity (CONT HIGH) | decrease | blood glucose | adults with type 1 diabetes | - | caused consistent acute glycaemic declines | #3 |
interval training (intermittent high-intensity exercise [IHE]) | decrease | blood glucose | adults with type 1 diabetes | - | caused consistent acute glycaemic declines | #4 |
high-intensity interval training (HIIT) | decrease | blood glucose | adults with type 1 diabetes | - | caused consistent acute glycaemic declines | #5 |
continuous exercise of high intensity (CONT HIGH) | decrease | acute glycaemic declines | adults with type 1 diabetes | - | largest effect size for | #6 |
high-intensity interval training (HIIT) | decrease | acute glycaemic declines | adults with type 1 diabetes | - | smallest effect size for | #7 |
pre-exercise mealtime insulin reductions | increase | blood glucose levels | adults with type 1 diabetes | - | created higher starting | #8 |
pre-exercise mealtime insulin reductions | decrease | hypoglycaemia | adults with type 1 diabetes | - | protecting against | #9 |
higher intensity postprandial exercise | increase | nocturnal hypoglycaemia | adults with type 1 diabetes | - | occurred after | #10 |
post-exercise snack with concomitant bolus insulin reduction | decrease | risk of nocturnal hypoglycaemia | adults with type 1 diabetes | - | could be diminished by | #11 |
People with type 1 diabetes experience challenges in managing blood glucose around exercise. Previous studies have examined glycaemic responses to different exercise modalities but paid little attention to participants' prandial state, although this is an important consideration and will enhance our understanding of the effects of exercise in order to improve blood glucose management around activity. This review summarises available data on the glycaemic effects of postprandial exercise (i.e. exercise within 2 h after a meal) in people with type 1 diabetes. Using a search strategy on electronic databases, literature was screened until November 2022 to identify clinical trials evaluating acute (during exercise), subacute (≤2 h after exercise) and late (>2 h to ≤24 h after exercise) effects of postprandial exercise in adults with type 1 diabetes. Studies were systematically organised and assessed by exercise modality: (1) walking exercise (WALK); (2) continuous exercise of moderate intensity (CONT MOD); (3) continuous exercise of high intensity (CONT HIGH); and (4) interval training (intermittent high-intensity exercise [IHE] or high-intensity interval training [HIIT]). Primary outcomes were blood glucose change and hypoglycaemia occurrence during and after exercise. All study details and results per outcome were listed in an evidence table. Twenty eligible articles were included: two included WALK sessions, eight included CONT MOD, seven included CONT HIGH, three included IHE and two included HIIT. All exercise modalities caused consistent acute glycaemic declines, with the largest effect size for CONT HIGH and the smallest for HIIT, depending on the duration and intensity of the exercise bout. Pre-exercise mealtime insulin reductions created higher starting blood glucose levels, thereby protecting against hypoglycaemia, in spite of similar declines in blood glucose during activity between the different insulin reduction strategies. Nocturnal hypoglycaemia occurred after higher intensity postprandial exercise, a risk that could be diminished by a post-exercise snack with concomitant bolus insulin reduction. Research on the optimal timing of postprandial exercise is inconclusive. In summary, individuals with type 1 diabetes exercising postprandially should substantially reduce insulin with the pre-exercise meal to avoid exercise-induced hypoglycaemia, with the magnitude of the reduction depending on the exercise duration and intensity. Importantly, pre-exercise blood glucose and timing of exercise should be considered to avoid hyperglycaemia around exercise. To protect against late-onset hypoglycaemia, a post-exercise meal with insulin adjustments might be advisable, especially for exercise in the evening or with a high-intensity component.