Hormonal Control of Energy and Macronutrient Intake in Obesity (MEMORY)

45 people (age 18-45 years old) with normal weight (BMI between 18.5-24.9 kg/m\^2, n=15), overweight (BMI between 25-29.9 kg/m\^2, n=15), and obesity (BMI above 30 kg/m\^2, n=15) will participate in this randomized cross-over study. Participants will complete one screening visit and two test visits.

During their test visits participants will be served a liquid meal consisting of either carbohydrate (sucrose) or protein (whey protein) diluted in water and sugar-free cordial mix for flavor. Participants will be served either carbohydrate or protein at their first visit and the opposite at their second visit in random order. The test visits will include clinical assessment (body weight, body composition, and blood pressure); Blood samples; Visual analogue scales for assessment of subjective appetite; Ad libitum buffet for assessment of energy intake. Participants will complete the Steno Biometric Food Preference Task (SBFPT), a computerized task measuring food choice, explicit liking, and implicit and explicit wanting with concomitant biometric measurements.

Time: -60 minutes (fasting), 0 minutes (liquid test meal), 150 minutes (ad libitum test buffet).

Descriptive data will be collected at the screening visit and will include body weight (kg); BMI, kg/m\^2; Fasting blood samples; Urine sample (future research); Adipose tissue biopsy (future research). Participants will also answer questionnaires regarding Socioeconomic status (SES), Control over eating (CoEQ), Health and wellbeing (SF-36), physical activity (international physical activity ((IPAQ)), and chronotype (morningsness/eveningsness ((MEQ)).

The specific research aims are:

1. To investigate whether intake of high-sucrose or high-protein affects subsequent food sensory-specific preference and different food intake from an ad libitum buffet, and whether this differs between individuals across the BMI range from normal weight to obesity. 2. To investigate whether the plasma FGF21 and glucagon responses:

1. Differ between the above-mentioned macronutrient compositions, 2. Are associated to subsequent food sensory-specific preference and macronutrient intake from an ad libitum buffet, and 3. Differ between individuals across the BMI range from normal weight to obesity. 3. To investigate whether the postprandial responses of well-known appetite-related hormones, as well as unexplored metabolites and proteins:

1. Differ between the above-mentioned macronutrient compositions, 2. Are associated to subsequent food sensory-specific preference and macronutrient intake from an ad libitum buffet, and 3. Differ between individuals across the BMI range from normal weight. 4. To identify new biomarkers facilitating patient stratification and optimize future treatment of obesity.

• Difference in self-reported energy intake [Time frame: Measured 24-hours after test visits]
• Difference in energy intake from fat [Time frame: Measured after meal consumption at t=150 min]
• Difference in energy intake from sweet tasting carbohydrates. [Time frame: Measured after meal consumption at t=150 min]
• Difference in energy intake from protein [Time frame: Measured after meal consumption at t=150 min]
• Food choice [Time frame: Measured during test visits (T=-60 min and T=120 min)]
• Food attention [Time frame: Measured during test visits (T=-60 min and T=120 min)]
• Food reaction time [Time frame: Measured during test visits (T=-60 min and T=120 min)]
• Explicit liking [Time frame: Measured during test visits (T=-60 min and T=120 min)]
• Implicit wanting [Time frame: Measured during test visits (T=-60 min and T=120 min)]
• Explicit wanting [Time frame: Measured during test visits (T=-60 min and T=120 min)]
• Unspecified exploratory outcome [Time frame: Measured during test visits (T=-60 min and T=120 min)]
• Subjective appetite sensations [Time frame: Measured at specific time points during test visits (fasted, T=15 min, T=30 min, T=60 min, T= 75 min, T=90 min, T=105 min, T=120 min, T=150 min)]