SucroMet Nutritional Intervention Trial

SucroMet is designed to evaluate how adding two commonly used sweeteners-sucrose (table sugar) and sucralose (a low-calorie sweetener)-at low and high doses may influence glucose regulation, including insulin resistance and fasting plasma glucose, in adults aged 18 to 65 years with normal weight, overweight, or obesity. The low-dose intervention consists of 5% of the Estimated Energy Requirement (EER) from sucrose or 5 sucralose tablets per day (approximately 33.35 mg/day of sucralose). The high-dose intervention consists of 10% of EER from sucrose or 10 sucralose tablets per day (approximately 66.7 mg/day of sucralose). These doses maintain the planned 1:2 exposure ratio between the low- and high-dose intervention groups. Before the intervention begins, participants' habitual dietary intake is assessed and, when necessary, minor dietary adjustments are made to support a stable overall eating pattern while maintaining energy intake. Participants then complete a four-week run-in period during which these recommendations are followed, and dietary records are used to verify dietary stability before the intervention starts. Participants will consume the assigned sweetener incorporated into foods or beverages that they already consume as part of their habitual diet, without substantial changes to their usual eating patterns. The intervention includes two consecutive 12-week phases, one involving solid food intake and the other involving liquid intake, separated by a two-week washout period. This design allows evaluation of the effects of sweetener type, dose, and mode of consumption. The primary outcomes are changes in glucose regulation, including fasting plasma glucose and insulin resistance assessed by HOMA-IR. Secondary outcomes include changes in body composition, anthropometric measurements, blood pressure, routine biochemical parameters, gut microbiota composition, DNA methylation patterns in peripheral blood cells, and biomarkers related to inflammation, oxidative stress, and metabolomic profiles measured in blood and urine. Participants will attend scheduled study visits for anthropometric assessments, dietary evaluations, and biological sample collection. Blood, urine, and stool samples will be obtained at baseline and after each intervention phase. The study aims to address the following questions: 1. Do metabolic responses to sucrose and sucralose, including changes in insulin resistance (HOMA-IR) and fasting plasma glucose, differ according to participants' body mass index (BMI)? 2. Do low and high doses of sucrose and sucralose differentially affect glucose regulation, body composition, and metabolic health? 3. Does the mode of intake (solid versus liquid) influence changes in gut microbiota composition? 4. Are changes in DNA methylation patterns in peripheral blood cells associated with the consumption of sucrose and sucralose at different doses and in different forms? 5. Do different doses of sucrose and sucralose influence biomarkers related to inflammation, oxidative stress, and metabolomic profiles?

Inclusion Criteria: * Adults aged 18 to 65 years at the time of enrollment. * Body Mass Index (BMI) between 18.5 and 39.9 kg/m². * Men and women who report a preference for sweet taste and habitual consumption of sugar and/or sweeteners. * Individuals in good general health, as determined by: 1. Medical history and clinical evaluation; 2. Absence of uncontrolled chronic diseases, such as diabetes, metabolic syndrome, severe hypertension, or advanced liver or renal disease; and 3. Baseline biochemical parameters within normal reference ranges, including fasting plasma glucose \