Strong scientific evidence supports the beneficial effects of exercise on cardiovascular health, the regulation of glucose metabolism, and fat oxidation. Physical performance capacity is known to fluctuate throughout the day, however, it is unknown whether there is an optimal time of day to maximize the effects of exercise on health, and specifically on blood glucose metabolism and fat oxidation. Finding the ideal time to perform physical exercise is of clinical and public health interest. Likewise, optimizing the timing of physical exercise to coincide with the greater physiological response of each individual would mean increasing the potential of exercise as a therapeutic tool.~Specific aims of this project are a) to describe possible differences dependent on sex and weight in the diurnal variation of the effect of exercise on glycemic metabolism and fat oxidation, and b) to characterize the molecular mechanisms implicated.~40 young adults with normal weight (50% females), and 40 young adults with obesity (50% females) will be randomized into two conditions (morning and evening) with at least 3 days of separation in between. Each evaluation will conform the following tests:~Basal metabolic rate assessment through indirect calorimetry.~Fuel oxidation and energy expenditure assesment during a 60 minutes bout of aerobic steady-state exercise (cycling), through indirect calorimetry.~Fuel oxidation and energy expenditure assesment after exercise during 60 minutes, through indirect calorimetry.~Blood samples assesment before, inmediately after, and 60 minutes after exercise.~Quadriceps biopsies before, inmediately after, and 60 minutes after exercise. *This will be done only in a sub-cohort of 32 participants.~Visual analog scales to assess appetite before, inmediately after, and 60 minutes after exercise.~Continous glucose monitoring from the first session day until14 days past.~Previous to this, participants' body composition and fitness level will be assesed via densitometry and a maximal exercise test, respectively.
The main objective of this project is to study the diurnal variation of the effect of exercise on glycemic metabolism and fat oxidation in humans.