The worldwide increase in the prevalence of obesity is a cause of great concern. Pharmacological treatment options are being explored at the moment with a major focus on the hormones produced by the gastrointestinal tract which regulate hunger and satiation/satiety. Modulating the release of these hormones via bitter substances reduced appetite-related sensations and gastrointestinal motility in lean female volunteers.

Intragastric administration of a quinine-solution has shown to decrease hunger sensations in healthy female volunteers. Now, we want to examine whether this effect is still seen in an overweight female population.

The aim of this study is to investigate the effect of acute administration of quinine hydrochloride on the consumed milkshake volume, gastrointestinal hormone levels, appetite-related sensations and whole blood glucose levels in overweight female individuals.

This study is a randomized, placebo-controlled, double blinded, cross-over study. Forty healthy overweight females will be recruited. An acute dose of 320 mg of quinine hydrochloride is administered as a solution via a nasogastric feeding tube. Blood samples will be collected at regular time points to measure gastrointestinal hormone release and whole blood glucose levels. Appetite related sensations will be scored at regular time points on visual analogue scales.

Inclusion Criteria:

• Subject is female between 18 and 65 years of age.
• Subject has a BMI between 25 and 30 kg/m² and has a stable body weight for at least 3 consecutive months at the start of the study and keeps a stable weight during the study visits.
• Women of child-bearing age agree to apply during the entire duration of the trial a highly effective method of birth control, which is defined as those which result in a low failure rate (i.e., less than 1% per year) when used constantly and correctly such as implants, injectables, combined oral contraceptive method, or some intrauterine devices (IUDs), sexual abstinence, or vasectomized partner. Women of non-childbearing potential may be included if surgically sterile (tubal ligation or hysterectomy) or postmenopausal with at least 2 year without spontaneous menses.
• Subject understands the study procedures and agrees to participate in the study by giving written informed consent.

Exclusion Criteria:

• Subject is under age of legal consent, male, pregnant or breastfeeding.
• Subject with a BMI ≤ 25 kg/m² or BMI ≥ 30 kg/m².
• Subject has current symptoms or a history of gastrointestinal or other significant somatic or psychiatric diseases or drug allergies.
• Subject is currently following a weight loss diet or other treatment for obesity.
• Subject has diabetes.
• Subject has a significant heart, lung, liver or kidney disease.
• Subject has a QT-interval > 450 ms.
• Subject has any history of a neurological disorder.
• Subject has a history of abdominal surgery. Those having undergone a simple appendectomy more than 1 year prior to the screening visit may participate.
• Subject has retinopathy.
• Subject suffers from psoriasis.
• Subject has porphyria.
• Subject has a hematologic disorder (e.g. hemolysis, thrombocytopenia).
• Subject shows abnormal eating behavior or has a history of an eating disorder.
• History or current use of drugs that can affect glycaemia, gastrointestinal function, motility or sensitivity or gastric acidity.
• History or current use of centrally acting medication, including antidepressants, antipsychotics and/or benzodiazepines (in the last year before screening visit).
• Subject consumes excessive amounts of alcohol, defined as >14 units per week.
• Subject is currently (defined as within approximately 1 year of the screening visit) a regular or irregular user (including "recreational use") of any illicit drugs (including marijuana) or has a history of drug (including alcohol) abuse. Further, patient is unwilling to refrain from the use of drugs during this study.
• High caffeine intake (> 4 cups of coffee daily or equivalent).
• Inability or unwillingness to perform all of the study procedures, or the subject is considered unsuitable in any way by the principal investigator.

Female volunteers are lingually more sensitive for the bitter taste compared to males. There are indications that also in the gut, the response is stronger in female volunteers than men.