High-intensity Intermittent Training for Obese Individuals

Participants will be randomized to one of three groups: HIIS (8s sprint:12s rest) or MICC (control group) iso-caloric protocols (for the duration needed to induce a 250 kcal energy deficit) or SDS (8s sprint:12s rest) for 10 minutes for 12 weeks. The intervention groups will be matched for age, BMI and male/females ratio and participants will be asked not to change their normal diet throughout the study. Before and after the exercise intervention (12 weeks), participants will perform the following assessments: 1. Three-day food diaries 2. Anthropometric measurements (weight, height, waist and hips) using standard procedures; 3. Body composition using dual energy x-ray absorptiometry (DEXA) 4. RMR and resting respiratory exchange ratio (RER) using indirect calorimetry; 5. Endothelial function assessed by flow-mediated dilation (FMD) of the brachial artery using vascular ultrasound according to current guidelines; 6. Maximal oxygen uptake (VO2max) and fat oxidation, cardiac output and left ventricular function during exercise using a cycle ergometer; 7. Muscle and fat biopsies 8. Fasting and postprandial release of appetite related hormones (and subjective feelings of hunger/fullness using visual analogue scales - VAS).