Molecular Landscape of Complex Lifestyle Modification

The goal of this clinical trial is to detect the impact of the 3-month complex lifestyle intervention, consisting of dietary counselling, supervised exercise training and cognitive-behavioural intervention in middle-aged sedentary individuals with obesity, specific questions are: * What is the adaptive response to exercise training on the whole-body and skeletal muscle energy metabolism, insulin sensitivity, metabolic flexibility, muscle functional parameters and cardiopulmonary fitness? * Would the intensity-related changes of the exercise-induced substrate preference (lipids vs carbohydrates) be a good predictive marker of metabolic flexibility i.e. the capacity to reduce the whole-body metabolic burden in patients with obesity? * Is the signal driving the adaptive response to regular exercise contained in serum derived Extracellular vesicles? Researchers will examine effects of exercise training intervention on whole body energy metabolism, by integrating clinical, biochemical and molecular data. Participants will: * Undergo 3 months exercise - intervention program. * Be submitted to examination of their obesity, energy metabolism and cardiopulmonary fitness related phenotypes using bioelectric impedance, indirect calorimetry, cycle spiroergometry. * Blood samples will be taken both, at the baseline PRE- and POST- intervention.