Weight loss is a cornerstone of diabetes (T2D) management, yet in clinical practice, its delivery is limited by its perceived burdensome nature and variability in response. Personalization of the interventions to increase their success rate is an unmet clinical need. The proposed project MEPHISTO (Whole body and gut microbiome metabolic flexibility to predict lifestyle intervention outcomes) would aim to identify predictive features related to successful weight loss upon sequential exercise and diet intervention in people living with obesity. To this end, the study aims to conduct a clinical trial where the investigators would implement state-of-the-art physiological phenotyping of metabolic flexibility at the whole-body level and at the level of the gut in persons with obesity before and after exercise and diet + exercise intervention to identify predictive signatures of successful weight loss