The goal of this intervention trial is to assess the effects of intermittent fasting, both alone and in combination with high-intensity interval training, on patients with obesity and metabolic syndrome. The main question it aims to answer is: Does intermittent fasting, with or without high-intensity interval training, reduce chronic inflammation in patients with obesity and metabolic syndrome? Participants will follow an intermittent fasting regime for 3 months, with one intervention group additionally participating in high-intensity interval training twice a week. In addition, there are two control groups: one consisting of participants with metabolic syndrome and one consisting of generally healthy individuals. The study includes a 3-month intervention phase followed by a 3-month follow-up phase. During the 6-month study period, all participants will attend 6 in-house study visits and 2 phone visits, during which they will undergo assessments and receive nutritional counseling.