Acute Microbial Switch

Inclusion Criteria: * Lean normoglycemic individuals: * Lean (BMI ≥ 18.5 kg/m2 and ≤ 24.9 kg/m2 ); * Normal fasting glucose (plasma glucose \< 5.6 mmol/L) and a HOMA-IR\< 2.2 Individuals with overweight/obesity and prediabetes/insulin resistance: * Overweight/obesity (BMI ≥ 28 kg/m2 and ≤ 40 kg/m2 ); * insulin resistance (HOMA-IR\>2.2) and/or impaired fasting glucose (IFG: plasma glucose ≥ 5.6 mmol/l) For both subject groups: * Aged 30 - 75 years; * Normal blood pressure (systolic blood pressure 100-150mmHg, diastolic blood pressure 60-100 mmHg); * Weight stable for at least 3 months (± 2 kg) Exclusion Criteria: * T2DM (defined as fasting plasma glucose ≥ 7.0 mmol/L) * Gastroenterological diseases * Abdominal surgery affecting the GI tract; * Cardiovascular diseases, cancer, liver or kidney malfunction, disease with a life expectancy shorter than five years; * Abuse of products; * Alcohol (\> 15 standard units per week) * Drugs * Excessive nicotine use defined as \>20 cigarettes per day; * Plans to lose weight or following of a hypocaloric diet * Regular supplementation of pre- or probiotic products, use of pre- or probiotics three months prior to the start of the study; * Intensive exercise training more than three hours a week; * Use of most medications that influence glucose or fat metabolism, like some lipid lowering-drugs (e.g., PPAR γ or PPARα (fibrates) agonists), glucose-lowering agents (including all sulfonylureas, biguanides, α-glucosidase inhibitors, …