An Integrative Study of the Role of Microbiome, Metabolome, Transcriptome and Chronobiology in the Context of Type 2 Diabetes.

The goal of this descriptive clinical study is to investigate daily oscillations in glycaemic control between healthy adults and adults with excess weight and who have early-stage prediabetes or T2D and are not taking medications for glycaemic control. The study also explores how these differences relate to changes in daily patterns in oral microbiome and metabolome, circadian markers, and lifestyle factors such as eating, physical activity, light exposure and appetite. The main questions to answer are: 1. Do adults with excess weight and prediabetes/T2D exhibit a disruption of the circadian system compared to healthy individuals? If so, are these disruptions manifested in hormone levels, gene expression, microbiota composition and function, metabolite levels and appetite regulation? 2. Does chrono-disruption contribute to the dysregulation of glucose metabolism and responses to lifestyle factors in individuals with excess weight and prediabetes/T2D? Researchers will compare two groups: * Healthy adults with normal weight. * Adults with excess weight (overweight or obesity) with prediabetes/T2D who are not on diabetes medications. The study will involve both semi-controlled settings (where food intake and physical activity are controlled) and free-living conditions. Participants will: * Wear devices: Use a continuous glucose monitor and a circadian monitoring device for 14 days. * Attend clinical visits: Visit the Nutritional Intervention Unit (NIU) 4 times for body composition measurements, sample collection (blood, saliva a faeces) and to answer questionnaires. . * Participate in a 12.5-hours clinical visit day in the NIU under semi-controlled conditions, with the purpose of collecting blood samples before and after breakfast and saliva samples every 4 hours, covering a full 24-hour cycle. * Keep track of daily habits: Maintain their usual lifestyle while keeping a food diary and recording appetite related feelings.