The goal of this double-blinded randomized clinical cross-over trial is to investigate the metabolic and appetite regulating effects of oral tributyrin (a butyrate pro-drug) administration vs placebo.

The main questions it aims to answer are:

• Does tributyrin have glucose lowering properties in humans?
• Does tributyrin reduce appetite in humans?

A sample size calculation estimated a minimum of 10 participants. We expect to include 12 participants in this study. Tributyrin or placebo is ingested once or twice daily for 2x2 weeks, separated by a washout period of minimum 2 weeks. On trial day following each 2-week period we assess:

• Postprandial blood sugar levels
• Hunger sensations (questionnaire)
• Enteroendocrine hormone secretion (GLP-1, GIP, PYY, LEAP2, ghrelin)
• Cardiac function (echocardiography) - An exploratory study evaluating the hemodynamic effects assessed by echocardiography is anticipated to be published separately.
• Caloric intake (ad libitum meal test)
• Gastric emptying rate (acetaminophen test)
• Resting metabolic rate (indirect calorimetry).

While at home, subjects will wear a sleep monitoring device for three consecutive nights and deliver fecal samples for analysis of short-chain fatty acid content and microbiota composition.

Inclusion Criteria:

• A body mass index (BMI) between 30-45 kg/m2
• Older than 18 years of age
• HbA1c < 48 mmol/mol
• Hemoglobin within normal range (females: 7.3-9.5 mmol/L, males: 8.3-10.5 mmol/L)
• Written and oral consent to participate

Exclusion Criteria:

• Medications affecting glucose metabolism and/or appetite (e.g. insulin, metformin, GLP-1 analogues)
• Special diet (HCLF, ketogenic diets, vegan/vegetarian)
• Ongoing cancer or other acute/chronic serious diseases (determined by PI)
• Inability to understand Danish or English
• Abnormal blood samples at screening visit (determined by PI and co-investigators)
• Deemed unsuitable to participate by the PI and co-investigators

The corresponding author will make data available on reasonable request.