The goal is to study the direct effects of long-term intermittent fasting on immune cell populations in the blood, combined with analyses of systemic metabolic fitness and inflammatory activation of leukocytes.

the investigators aim to investigate the direct effects of intermittent fasting on the molecular characteristics of monocytes and their related health benefits. In addition,the investigators want to assess the post-prandial inflammation and the potential protective role of IF on post-prandial monocyte activation and its related health benefits. This pilot study may better understand the molecular mechanisms behind IF, which could further personalize lifestyle guidance and identify novel anti-inflammatory processes that control immune responses and inflammation.

Inclusion Criteria metsyn:

• BMI 30 to 43 kg/m2
• HOMA-IR index larger/same as 2.5
• And At least 3 out of 5 NCEP (National Cholesterol Education Program) metabolic syndrome criteria:
• Fasting plasma glucose ≥ 6.1 mmol/l,
• Triglycerides≥1.7mmol/l,
• Waist-circumference>102cm,
• HDL-cholesterol<1.04mmol/l,
• Bloodpressure≥130/85mmHg).

Inclusion healthy volunteers

• Body mass index (BMI) 18 to 25 kg/m2,
• Waist circumference between 79 cm and 94 cm and
• HOMA-IR index: ≤ 2.0 (measured as fasting insulin (pmol/L) x fasting glucose (mmol/L)) / 135)

Exclusion criteria; (all)

• Excessive weight loss of >10% in the last months;
• Use of any medication, including proton pomp inhibitors and antibiotics in the past three months;
• Cholecystectomy;
• Untreated GI disease/abnormal bowel habits;
• Plasma aspartate aminotransferase and alanine aminotransferase are 2.5 times or more the upper limit of the normal range;
• A history of cardiovascular event (MI or pacemaker implantation);
• A history of heavy alcohol use (>12 to 15 g of alcohol per day, or >12 oz of beer, 5 oz of wine, or 1.5 oz of distilled spirits);
• A dependency on alcohol or unable to pause the consumption of alcohol during the study period.
• An (expected) prolonged compromised immunity (due to recent cytotoxic chemotherapy or HIV infection with a CD4 count < 240);
• Unmotivated or not able to adhere to a specific diet;
• History of eating disorder;
• Night workers or people with deviant day/night rhythm;
• Pregnant, trying to get pregnant or breast feeding at inclusion;
• Irregular menstrual cycle;
• Hormonal replacement therapy (other than oral contraceptives).

Investigators analysing study outcomes will be blinde