12 obese subjects will receive peripheral administration of placebo and 4 escalating doses of PYY1-36 and another 12 obese subjects will receive peripheral administration of placebo and 4 escalating doses PYY3-36 on 5 different test days within one week. The patients will be tested in a single blinded dose escalating protocol. Measurements of appetite, ad libitum energy intake, blood pressure and blood sampling will be performed during the test day.

Inclusion Criteria:

• Normal weight (BMI: 18-23 kg/m2) or 12 overweight/obese (BMI: 27-40 kg/m2)
• Body weight fluctuations < 5 kg over the past 2 months.
• Blood pressure normal to mildly hypertensive(<159/99 mm Hg)
• Non-elite athletes and not planning to change physical activity during the study.

Exclusion Criteria:

• Any physiological or psychological illnesses that could influence the study results.
• Regular use of medicine.
• Smoking defined as <1 cigarette per day.
• Substance abuse or dependence.
• Blood donation within the past 3 months before entering the study.
• Drinking >21 alcoholic units/week.
• Food allergies.
• Special diets (e.g. vegetarian) or dislikes to any of the foods served during the study.