13th April 2025, A/Prof Chee L Khoo
Continuous glucose monitoring (CGM) was first shown to be beneficial in the management of patients with type 1 diabetes. Later on, patients with type 2 diabetes on insulin also found CGM beneficial in more ways than one. Of course, patients with T2D not on insulin also found CGM beneficial. What else can we use CGM for? Well, a group of clinicians from Wollongong thought we could use CGM to determine whether exercise prior to an expected hyperglycaemia can prevent the hyperglycaemia (1). If we can prevent hyperglycaemic excursions, we might be able to prevent metabolic damage.
While HbA1c is the “gold” standard in measuring glycaemic control, since the advent of CGM, large glucose excursions and glucose variability are increasingly being independently associated with the development of diabetes complications including cardiovascular diseases. Hyperglycaemic peaks and fluctuations in glucose levels causes oxidative stresses to the endothelium. Reducing these excursions have been shown to improve cardiovascular risks.
Regular exercise is an important component of diabetes management and treatment. People with diabetes are recommended to accumulate at least 150–300 min of moderate-intensity aerobic activity per week, in addition to two or more strengthening activities per week [2]. Exercise promote muscle uptake of glucose and help to lower blood glucose levels. Patients with diabetes have different dietary patterns, different fitness levels and different degrees of insulin sensitivity at the muscle level. Exercising during the postprandial period (approximately three hours after a meal) is considered the most effective time to reduce peak hyperglycaemia [3-6]. However, it remains unclear when during this postprandial period is best to start exercising, and which meal of the day should precede the exercise session [3,4].
This is where CGM comes very handy. Courtney Chang et al conducted randomised controlled trial investigated the impact of utilising CGM to personalise exercise timing on peak hyperglycaemia and cardiometabolic health in people with T2D. Adults with T2D were randomised to:
- Control – usual care, usual exercise routine for 8 weeks then randomised to intervention grpoups
- 22-min daily exercise commencing 30 mins before peak hyperglcyaemia (determine by 14 days of CGM readings prior to start of trial) – ExPeak group
- 22-min daily exercise 90 mins after peak hyperglcyaemia – NonPeak group
Glycaemic control (HbA1c [primary outcome], CGM), vascular function (flow-mediated dilation [FMD]), arterial stiffness, blood pressure) and body composition were assessed.
Vascular health and body composition were assessed for in-person participants (as previously described [24]). Briefly, vascular assessments included: i) endothelial function, assessed by measuring brachial artery flow-mediated dilation using ultrasound imaging and ii) blood pressure and central arterial stiffness, assessed using the SphygmoCor® XCEL System (AtCor Medical Pty. Ltd., Sydney, Australia) measuring pulse wave analysis (PWA) and pulse wave velocity (PWV).
The intervention
Adherence to the prescribed duration and exercise time was self- reported during each telehealth call and calculated as a percentage of the average number of sessions participants completed throughout the eight-week intervention. Adherence to the aerobic physical activity guidelines was calculated as the number of times participants reported accumulating at least 150 min/week of aerobic exercise. Barriers for missing exercise sessions were reported at each telehealth call and were dichotomized into four categories including: scheduling conflicts, extreme weather conditions, unrelated illness or injury, and low energy.
Results
A total of 459 individuals were screened for inclusion from July 2019 to October 2022. Of these, 377 were excluded primarily due to the following: 1) HbA1c < 6.5 %, 2) > 150 min/week of moderate to vigorous intensity aerobic activity, 3) diagnosed CVD, 4) recent change in medications, and 5) HbA1c > 9.1 %. A total of 82 individuals were enrolled.
Not unexpectedly, because of the short time frame of only 8 weeks, there were no effect of the intervention on HbA1c, however 24 hour peak and mean glucose were reduced, and endothelial function improved in both intervention groups prescribed a time to exercise.
Overall, prescribing a time to exercise (irrespective of when) led to improvements in CGM-derived measures of glycaemic control and endothelial function compared to no prescribed exercise time in the control group. Both intervention groups reported adhering to 90 % of their daily exercise sessions, with 77 % indicating that they met the aerobic recommendation of at least 150 min per week.
There was a significant difference between the ExPeak and control group in the waist hip ratio. The ExPeak group lost by 1.3kg while the NonPeak and control groups only lost 0.5kg. There were no changes in lean or fat mass between the group.
Implications
This study highlighted that specific personalised exercise prescription may improve adherence. Tailoring the exercise advice according to CGM data makes sense and not only reduce hyperglycaemic excursions but may also improve patients adherence to diet and exercises. We already know that the patient’s awareness of glucose readings improve dietary adherence. Despite the cost of CGM, there is a gradual uptake of this technology and we should utilise the data for a good cause.
References
- Chang CR, Roach LA, Russell BM, Francois ME. Using continuous glucose monitoring to prescribe an exercise time: a randomised controlled trial in adults with type 2 diabetes. Diabetes Res Clin Pract. 2025 Apr;222:112072.
- Bull FC, Al-Ansari SS, Biddle S, et al. World Health Organization 2020 guidelines on physical activity and sedentary behaviour. Br J Sports Med 2020;54:1451–62.
- Teo SY, Kanaley JA, Guelfi KJ, et al. Exercise timing in type 2 diabetes mellitus: a systematic review. Med Sci Sports Exerc 2018;50:2387–97.
- Borror A, Zieff G, Battaglini C, Stoner L. The effects of postprandial exercise on glucose control in individuals with type 2 diabetes: a systematic review. Sports Med 2018;48:1479–91.
- Aqeel M, Forster A, Richards EA, et al. The effect of timing of exercise and eating on postprandial response in adults: a systematic review. Nutrients 2020;12:221.
- Engeroff T, Groneberg DA, Wilke J. After dinner rest a while, after supper walk a mile? A systematic review with meta-analysis on the acute postprandial glycemic response to exercise before and after meal ingestion in healthy subjects and patients with impaired glucose tolerance. Sports Med 2023:1–21.