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ACUTE HEAT EXPOSURE LOWERS POSTPRANDIAL GLUCOSE & GLYCEMIC VARIABILITY OF HEALTHY MALE & FEMALE COLLEGE STUDENTS

Abstract

Elevated postprandial glucose (PPG) is a robust measure of glycemic control and cardiometabolic health risk. While physical activity has been shown to reduce PPG, little is known about the effects of whole-body heat. PURPOSE: To determine the impact of heat and immediate postprandial walking on PPG in high-heat conditions in healthy individuals. METHODS: Eleven healthy non-obese (24.3 ± 3.7 BMI) adults (age 20-22, 7 females and 4 males) were fitted with continuous glucose monitors (CGMs, Abbott Freestyle Libre Pro) to measure interstitial glucose every 15 minutes. Following consumption of a standardized breakfast meal (547 kcal: 25% FAT, 10% PRO and 65% CHO, GI 74), participants randomly completed three trials in 25% humidity: (1) Temp-SED: seated sedentary for 90 mins at 20˚C, (2) Heat-SED: seated sedentary for 90 mins at 40˚C and (3) Heat-PA: walking on a treadmill (2.5-3 mph) for 20 mins, followed by seated recovery for 70 mins at 40˚C (Heat-PA). RESULTS: PPG area under the curve (AUC) was 13.7% lower in Heat-SED (8923 ± 1308 mg/dL/min, p=0.009, d=0.97) and 12.6% lower in Heat-PA (9017 ± 1516 mg/dL/min, p=0.04, d=0.71) compared to Temp-SED (10231 ± 1111 mg/dL/min). Mean absolute glucose (MAG) was 56.5% lower in Heat-PA (1.8 ± 0.9 mM) than Temp-SED (3.2 ± 1.2 mM, p = 0.017, d=0.87) and 45.3% lower in Heat-PA than Heat-SED (2.9 ± 1.0 mM, p=0.014, d=0.89). Coefficient of variation (CV), a measure of glycemic variability, was 40.6% lower in Heat-PA than Temp-SED (p = 0.041, d=0.7), and 28.8% lower than Heat-SED (p=0.02, d=1.1). CONCLUSIONS: A single bout of whole-body heat exposure (40˚C) effectively improved glycemic control via reduced PPG and glycemic variability in normoglycemic young adults. Our findings suggest that acute heat therapy could serve as an alternative modality to improve glucose control in mobility-limited individuals and the 75% of U.S. adults who do not meet physical activity guidelines. Future research is warranted to explore the efficacy of heat therapy in populations with impaired glucose tolerance and metabolic disorders, where the therapeutic benefits may be even more pronounced.

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