FLORA is a longitudinal intervention study with a randomized, parallel group design. Primary objective is to improve metabolic health through gut microbiota modulation by means of a retailer-driven personalized dietary intervention in a real-life setting. Four hundred Flemish pre-metabolic adults will be randomly divided into a control and treatment arm, each comprising 200 participants. The study period is divided into three phases: a four weeks characterization, a twelve weeks intervention, and a four weeks post-intervention phase. During the intervention phase, control participants' online Collect&Go shopping carts are adjusted in accordance with Flemish food-based dietary guidelines. Based on the same guidelines, participants are provided with personalized dietary advice considering their usual dietary pattern and level of food literacy. In the treatment arm, a similar intervention will be applied using guidelines based on a microbiota modulation diet (MMD). During intervention, all participants can contact a dietician helpline for additional advice on study-related dietary issues. Over the five months, saliva and fecal samples will be collected on a regular basis, with an intensive sampling period of seven consecutive days at the end of each study phase. A GP consult consisting of a short medical exam, blood withdrawal and medical questionnaire takes place each month. Further, online questionnaires on lifestyle, health and well-being will be sent by e-mail and each five days, participants complete a food diary through their smartphone. Fecal, saliva, blood samples and meta-data will be analysed to detect changes in metabolic health.

Inclusion criteria

• Willingness to participate to the study and to sign the informed consent (Dutch)
• Older than 18 years
• Diagnosed with pre-metabolic syndrome (diagnosed with central obesity [waist circumference ≥80 cm for women and ≥94 cm for men] and one of the following criteria: elevated blood pressure [systolic ≥130 mm Hg, diastolic ≥85 mm Hg], raised triglycerides [>150 mg/dL], reduced HDL-cholesterol [<40 mg/dL in men, <50 mg/dL in women], or raised fasting plasma glucose [≥100 mg/dL]
• Residing in Belgium, no travels abroad planned longer than seven consecutive days during the five-months study period
• Willingness to follow dietary guidelines during the three-months intervention period
• Willingness to purchase bulk groceries primarily at Colruyt Group using the Collect&Go platform during the five-months study period
• Access to a -20-18°C freezer

Exclusion criteria

• Chronic constipation (less than one defecation once a week)
• Gastro-intestinal surgery within the past 3 months
• Inflammatory bowel disease (IBD) or diverticulitis
• Irritable bowel syndrome (IBS)
• Any food allergy or food intolerance
• Metabolic syndrome
• Diabetes Mellitus Type 1 or Type 2
• Coeliac disease
• Pregnant women or women planning a pregnancy during the study period
• Lactating women
• Subjects on a specific diet (e.g. vegetarian/vegan diet, gluten-free diet, lactose-free diet, high-protein diet)
• Subjects being treated for hypertension or high cholesterol