In this project the investigators intend to study the therapeutic potential of a personalized fibre mixture in individuals at high risk of developing T2DM, and aim to address the following key objectives:

1. To investigate whether a mixture of fermentable fibres, which differ in DP and side chains, will stimulate a broad range of SCFA-producing bacterial genera, resulting in enhanced chronic SCFA production throughout the whole colon with a large variation between individuals;
2. To unravel whether providing personalized fibre mixtures, selected based on the individuals' initial microbiota and capacity for SCFA production is crucial to successfully improve host insulin sensitivity and metabolic health

Inclusion Criteria:

Overweight/obese insulin resistant/prediabetic participants (age 30-70 y, BMI ≥ 28 kg/m2 < 40 kg/m2)

Exclusion Criteria:

• Type 2 diabetes mellitus (defined as fasting plasma glucose ≥ 7.0 mmol/L and 2h glucose ≥ 11.1 mmol/L)
• Gastroenterological diseases or abdominal surgery;
• Cardiovascular diseases, cancer, liver or kidney malfunction, disease with a life expectancy shorter than 5 years;
• Abuse of products; alcohol and 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 3 months prior to the start of the study;
• Intensive exercise training more than three hours a week;
• Use of any medication that influences glucose or fat metabolism and inflammation (i.e. NSAIDs);
• Regular use of laxation products;
• Use of antibiotics in the last three months (antibiotics use can alter substantially the gut microbiota composition).
• Follow a vegetarian diet.