Gut Hormone LEAP2 in Metabolism and Eating Behaviour: Fixed Meal Testing

Inclusion Criteria: * Male or female between the ages of 18 and 60 years; * Without obesity with body mass index (BMI) 18.0-29.9 kg/m2 or with obesity with BMI 30.0-50.0 kg/m2; * Healthy as determined by medical history and vital signs; * Capable of giving written informed consent, which includes compliance with the requirements and restrictions listed in the consent form; * Participant is able to read, comprehend and record information written in English. Exclusion Criteria: * History of, or current abuse or dependence on alcohol or drugs; * Current smoker or less than 2 years since quitting (cigarette, cigars, e-cigarettes) or use of nicotine replacement therapy; * Significant current or past medical or psychiatric history that, in the opinion of the investigators, contraindicates their participation; * History of type 1 or type 2 diabetes mellitus; * History of ischaemic heart disease, heart failure, cardiac arrhythmia, peripheral vascular, cerebrovascular disease or uncontrolled hypertension; * Current diagnosis of anaemia or iron deficiency; * Body weight instability (change in body weight of more than 5% over the preceding 3 months); * Use of current regular prescription or over-the-counter medications that in the opinion of the Investigators may affect participant safety or outcome measures; * Clinically significant abnormalities in screening blood tests abnormalities which in the opinion of the study physician, is clinically significant e.g. diabetes mellitus, hypothyroidism, renal impairment, abnormal liver function tests \[bilirubin, alanine transaminase (ALT), aspartate transaminase (AST), gamma-glutamyl transferase (GGT)\] \>3x upper limit of normal, other than due to fatty liver disease; Current pregnancy or breast-feeding in female volunteers (the Investigators will recommend using contraception for the duration of the visits to avoid participant drop-out); * Pulse rate \<40 or \>100 beats per minute OR systolic blood pressure \>160 and \<100 OR diastolic blood pressure \>95 and \<50 in the semi-supine position; * Volunteer has participated in a clinical trial and has received an investigational product within the following time period prior to the first experimental visit in the current study: 90 days, 5 half-lives or twice the duration of the biological effect of the investigational product (whichever is longer); * Exposure to more than 3 new investigational medicinal products within 12 months prior to the scan; * Vegan, gluten or lactose-intolerant (as test meals in the paradigms may include animal products, dairy and wheat products); * Volunteers who have donated, or intend to donate, blood within three months before the screening visit or following study visit completion; * Known history of SARS-CoV-2 infection (Covid-19) in the last 4 weeks; * Ongoing symptoms suggestive of complications from previous SARS-CoV-2 infection ('long Covid-19') such as loss or change in sense of smell or taste, shortness of breath, palpitations, lethargy; * SCOFF questionnaire score \>1/5 indicating eating disorders (Luck et al. 2002); * DSM-V criteria for alcohol use disorder (AUD) \>2/11 indicating mild AUD (American-Psychiatric-Association 2013); * Participants who have had previous obesity surgery or are on medications for obesity; * Dutch Eating Behaviour Questionnaire (DEBQ) restraint score \>3/5 indicating highly restrained eating behaviour.