Association between Physical Activity Energy Expenditure and Continuous Glucose Monitor-Derived Metrics: Data from the ZOE PREDICT 1 Study ^†

Background and objectives: Physical activity can improve glucose variability (GV) and time in range (TIR) in people with impaired glucose tolerance/diabetes [1,2]. However, the effects of physical activity on these parameters in people within normo-glycaemic ranges are unclear. This study explores the associations between physical activity, GV, and TIR in normo-glycaemic individuals from the ZOE PREDICT 1 cohort. Methods: Free-living continuous interstitial glucose (using continuous glucose monitoring) and activity energy expenditure (AEE; mean of 14 days using a wrist-based accelerometer [ENMO]) were collected in the ZOE PREDICT 1 study (n = 1002). TIR was calculated using (1) the American Diabetes Association criteria (TIR 3.9–7.8 mmol∙L⁻¹) and (2) a novel ‘stringent’ range (TIR 3.9–5.6 mmol∙L⁻¹) [3]. The relationship between AEE and glycaemic outcomes (GV and TIR) was assessed using partial correlations (adjusted for age, sex, and BMI). Results: Data from 698 participants (186 M/512 F) were analysed (mean ± SD; age: 45 ± 12 y; body mass index (BMI): 25.4 ± 4.8 kg∙m⁻²; and estimated basal metabolic rate (BMR; Harris–Benedict equation): 1456 ± 225 kcal∙d⁻¹). The mean fasting glucose concentration was 4.93 ± 0.42 mmol∙L⁻¹ (range: 3.58–6.07 mmol∙L⁻¹), and the mean daily glucose concentration was 5.02 ± 0.54 mmol∙L⁻¹ (range: 3.43–7.19 mmol∙L⁻¹). The median GV was 16.1% (IQR: 13.1–18.5%), and the median proportion of time spent in TIR 3.9–5.6 was 72.4% (IQR: 62.0–80.7%) compared to 95.3% (IQR: 87.7–99.0%) in TIR ADA. AEE was inversely associated with TIR 3.9–5.6 (r = −0.09 p = 0.02), but not with TIR ADA (r = 0.03 p = 0.43), and positively associated with daily mean glucose concentration (r = 0.13, p < 0.001). Discussion: The data presented in this study suggest that, in normo-glycaemic individuals, higher activity energy expenditure is associated with a lower proportion of time spent within a novel ‘stringent’ range of interstitial glucose concentrations. However, the causality of this relationship is unclear, and future research should establish whether a higher physical activity level drives a higher glucose level, or vice versa.