Mechanisms Underlying Individual Variations of Taste and Smell in Obesity

Inclusion criteria

• In order to be eligible to participate in this study, an individual must meet all of the following criteria:
• Males and females between 18 to 65 years of age. Due to documented knowledge that taste and smell changes with age, we will limit the cohort within this age range.
• BMI between 18.5 and 29.9 kg/m\^2 for healthy controls or between 30 and 39.9 kg/m\^2 for obese subjects
• Fasted plasma glucose levels between 68-126 mg/dl or per Clinical Center ranges, and hemoglobin A1C\<6.5%
• Able to provide his/her own consent
• Able to understand the protocol, as shown by scoring a 6 out of 6 on a consent quiz

Exclusion criteria

• An individual who meets any of the following criteria will be excluded from participation in this study:
• Because type-2 diabetic subjects have blunted taste responses, subjects with diagnosis of type II diabetes will be excluded.
• Hypoglycemic drug intake.
• Weight change of more than 15 pounds in the 6 months prior to screening
• Positive pregnancy test, currently pregnant or breastfeeding.
• Currently using any of the following medications: steroidal or nonsteroidal antiinflammatory medications, medications known to inhibit taste response (GLP1 agonists), antiepileptic or antidepressant agents, glucocorticoids, or antibiotics.
• Received a diagnosis by a medical professional of morbid obesity, liver or renal disease.
• Individuals with current heavy drinking. Women who drink 4 drinks or more in one occasion and 7 drinks in a week. Men who drink 5 drinks or more in one occasion and more than 14 drinks a week.
• Use of tobacco products or illicit drugs (as determined by urine drug screen and/or history/physical exam) in the last 30 days.
• Currently have an uncontrolled medical disorder (i.e., gastrointestinal, endocrine, cardiac, psychiatric).
• Any self-reported history of chronic rhinitis, eating disorder (including binge eating), chronic upper respiratory infection, chronic allergic rhinitis, or nasal polyps in the last 6 months of screening, or current daily use of nasal sprays.
• Abnormal complete blood count (CBC): White Blood Cell Count \< 4 or \> 10 K/uL, Red Blood Cell Count \< 4 or \> 7 M/uL, Hemoglobin \< 12 g/dL for females or \< 13 g/dL for males or any clinical signs/symptoms that indicate iron deficiency anemia per clinician s judgment at screening \[National Heart, Lung and Blood Institute (NHLBI) definition (Anemia - Iron-Deficiency Anemia, Diagnosis NHLBI, NIH)\].
• Bariatric surgery within the last 12 months of screening.
• History of cancer (e.g., head and neck cancer) and/or history of cancer treatment (e.g., radiotherapy to the head and neck area or chemotherapy).
• Altered cranial nerves identified by neurological evaluation during physical exam (screening visit).
• Currently experiencing temporary change/loss of taste and/or smell.
• Persistent loss of taste and/or smell due to COVID-19 or other reasons.
• Unable to read and understand English. Since all self-report measures are in English only, participants need to be able to read and understand the English language.
• NIAAA employees/staff or subordinates/relatives/co-workers of NIAAA employees/staff or study investigators.