Impact of Acute High-Heat Exposure on 24-Hour Glycemic Variability in Healthy Female and Male College Students

Significance: Dysregulation of glucose homeostasis is a risk factor for cardio-metabolic disease. Continuous glucose monitoring (CGM) provides real-time assessment of glucose levels and can lead to improvements in glycemic control. While it is well established that physical activity improves glycemic control, the effects of whole-body heat on glucose control are not well known. Objective: To determine the impact of an acute bout of extreme heat on glucose variability in young non-obese healthy participants. We hypothesized that a single bout of whole-body heat exposure (40˚C) for 90-min would improve markers of glycemic variability over 24-hrs in healthy adults. Methods: Eight (4 females and 4 males) healthy non-obese college students (age 20-22) wore a CGM (Abbott Freestyle Libre Pro) for up to 14 days. Following an overnight fast, participants consumed a standardized breakfast meal of 547 kcal (25% FAT, 10% PRO, 65% CHO) and randomly completed two trials: (1) 90 minutes seated sedentary at 20˚C (TEMP-SED) and (2) 90 minutes seated sedentary at 40˚C (HEAT-SED). Markers of glycemic variability were assessed in the 24-hrs following each trial during free-living conditions: mean glucose, standard deviation (SD), coefficient of variation (CV), mean amplitude of glucose excursions (MAGE), continuous overlapping net glycemic action (CONGA), J-index, lability index (LI), and mean absolute glucose (MAG) were calculated using EasyGV© software. Results: During the 90-min following the mixed meal, glucose AUC was 12.8% lower in HEAT-SED (8923 ± 1308 mg/dL/min) compared to TEMP-SED (10230.7 ± 1111.2 mg/dL x min, p=0.009, d=0.97 ). 24-hour mean glucose trended to be 8.6% lower following HEAT-SED (4.9 ± 0.7 mM) than TEMP-SED (5.4 ± 0.2 mM, p=0.06, d=0.61 ). CONGA trended to be 9.3% lower following HEAT-SED (4.4 ± 0.7 mM) than TEMP-SED (4.8 ± 0.2 mM, p=0.06, d=0.59 ). Conclusion: A single 90-min bout of whole-body high-heat exposure reduces postprandial glucose and may improve markers of glycemic variability over the subsequent 24 hours in healthy normoglycemic adults. This sustained improvement in glycemic control during and following an acute bout of high-heat exposure may serve as a novel therapeutic approach for individuals with impaired glucose tolerance. This study was supported and funded by the Human Physiology Department, Gonzaga University. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.