The goal of this double-blinded, randomized cross-over clinical trial is to assess the isolated (i.e. outside the context of exercise) effects of Lac-Phe on appetite and glucose concentrations in healthy volunteers with obesity (BMI 28-35).

The main questions it aims to answer are:

• Does Lac-Phe reduce appetite in humans?
• Does Lac-Phe have glucose-lowering properties in humans?

During the study, participants will:

• receive an intravenous infusion of Lac-Phe on one study day and a NaCl infusion on another study day.
• drink a standard mixed meal
• eat an ad libitum meal test
• answer appetite questionnaires
• indirect calorimetry
• blood samples for hormone and substate analyses

Inclusion Criteria:

• A body mass index (BMI) between 28-35 kg/m2
• Older than 18 years of age
• Hgb within a normal range (females: 7.3-9.5 mmol/L, males: 8.3-10.5 mmol/L)
• Females can be included if they are either postmenopausal or actively use hormonal contraception (e.g., oral contraceptive pill or hormone-releasing intrauterine device).

Exclusion Criteria:

• Medications affecting glucose metabolism (e.g., Saxenda).
• Anemia
• Diabetes
• Ongoing cancer or other acute/chronic serious diseases (PI will determine)
• Inability to understand Danish or English
• Deemed unsuitable to participate by the PI and co-investigators.

The corresponding author will make data available on reasonable request.