The goal of this prospective interventional study is to examine if repeated brief hot stimuli affects glucose metabolism and substrate oxidation in young non-obese adults. Young adult participants were asked to participate in fourteen 5-min procedures involving whole body passive heating at 45°C water.

The main question it aims to answer is: "Does repeated brief noxious heat stimuli is sufficient to improve glucose tolerance, insulin sensitivity, and fat oxidation in young non-obese adults?"

No studies yet addressed whether brief heat stimuli could be viable time-efficient alternative approach in order to improve glucose metabolism and fat oxidation. Consequently, we aimed to examine the ability of brief noxious heat stimuli to improve glucose tolerance, insulin sensitivity, and fat oxidation in young adults. Non-obese males and females completed fourteen 5-min sessions involving whole body passive heating at 45°C water. Changes in catecholamines, cytokines, substrate oxidation, resting energy expenditure, glucose tolerance and insulin response were assessed.

Inclusion Criteria:

• healthy non-obese (BMI between 18.5 and 29.9 kg/m2) males and females;
• no diseases, or conditions that could be worsened by exposure to acute hot water and affect experimental variables;
• no participation in any excessive formal physical exercise or sports program, temperature manipulation program or exposure to extreme temperatures.

Exclusion Criteria:

• smokers;
• obesity (BMI greater than 30 kg/m2);
• needle phobia;
• taking medication and/or dietary supplements that may affect experimental variables.