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Mechanisms Underlying Individual Variations of Taste and Smell in Obesity

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Know the risks and potential benefits of clinical studies and talk to your health care provider before participating. Read our disclaimer for details. Identifier: NCT04714892
Recruitment Status : Not yet recruiting
First Posted : January 20, 2021
Last Update Posted : July 26, 2021
Information provided by (Responsible Party):
National Institutes of Health Clinical Center (CC) ( National Institute on Alcohol Abuse and Alcoholism (NIAAA) )

Brief Summary:


Changes to the sense of taste or smell can change eating behavior. This may contribute to obesity. Researchers want to see how taste and smell perceptions that affect food choices may differ between obese and non-obese people.


To understand the role that senses of taste and smell play in food intake.


Obese and non-obese adults ages 18-50


Participants will be screened with a medical history and physical exam. They will have a neurological and sensory exam. They will give blood and urine samples. They will be checked for previous SARS-CoV-2 infection. They will complete questionnaires about their eating habits, alcohol use, and smoking history.

Participants will have 2 study visits.

Participants will give stool, urine, blood, hair, nasal, and saliva samples. These samples will be used for gene testing.

Participants will have their weight, height, and hip and waist circumference measured. They will have an imaging scan that measures body composition.

Participants will complete questionnaires about their health, eating habits, and food preferences.

Participants will have taste tests and smell tests. They will have sensory tests to assess their response to stimuli.

Participants tongue papillae (the bumps on the surface of the tongue) will be counted. A blue dye will be put on their tongue, then a picture will be taken.

Participants taste function will be measured. They will taste different stimuli. A current will be passed through their tongue.

Participants will have a dietary assessment. They will complete a food diary and a diet history questionnaire.

Participants will get a meal to eat. Data will be collected about their experience.

Participants will complete a sleep diary.

Condition or disease

Detailed Description:

This study involves comparison of taste and smell measures between obese and non-obese individuals. Taste and smell perceptions will be assessed in terms of their influence in food intake and food choices. We hypothesize that obesity negatively affects taste and smell perception thus affecting eating behavior.

Obesity is a major public health concern in America. An unhealthy diet is a recognized risk factor for the development of obesity. Public health efforts to modify eating behaviors have had limited success. Not only does an unhealthy diet contribute to obesity, it can lead to changes in gut microbiota that likely result in inflammation and changes in transcriptomic activity. Taste and smell perceptions, which can influence food choices and food consumption, may differ between obese and non-obese individuals. Currently, little is known about the underlying mechanisms causing variations in taste and smell systems in individuals with obesity, which limits the interventions currently available to address this critical issue. Findings from this study can be used to design more effective interventions for the prevention and treatment of obesity, to identify targets and strategies for countermeasures to prevent or improve obesity and its comorbidities, and to suggest ways to enhance dietary interventions. Moreover, findings will foster new lines of investigation for reducing risk of diet-related conditions and for developing novel behavioral and pharmacological avenues of treatment and prevention. The proposed research is aligned with the overall mission of the National Institutes of Health to promote health and disease prevention. The findings from this study will ultimately lead to the development of personalized interventions for individuals with obesity and concurrent taste and smell alterations. Lastly, approaches included in this proposal are innovative and highly applicable to other complex health phenomena in which biological variations in inflammation and taste and smell perception impact an individual s health.

Primary Endpoint: The primary dependent measures for this study are taste and olfaction measures.

Secondary Endpoints: Secondary measures include inflammatory markers, exosomes, microbiota, gene expression, DNA methylation, biological measures and personal factors.

We will recruit a cohort of 124 obese individuals matched by age and sex with 124 healthy non-obese controls. Participants will be recruited from the Washington Metropolitan area and vicinity.

This study will take place at the NIH Clinical Center.

The study is expected to be completed in 60 months from opening of enrollment to study completion of data analysis.

This study involves one screening visit and 2 study visits. The screening visit will last approximately 4-5 hours. Visits 1 and 2 will take approximately 4-6 hours each to complete.

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Study Type : Observational
Estimated Enrollment : 248 participants
Observational Model: Case-Control
Time Perspective: Cross-Sectional
Official Title: Mechanisms Underlying Individual Variations of Taste and Smell in Obesity
Estimated Study Start Date : July 29, 2021
Estimated Primary Completion Date : December 30, 2022
Estimated Study Completion Date : December 30, 2022

Resource links provided by the National Library of Medicine

Healthy control
BMI of 18.5-29.9 kg/m2
BMI of 30-39.9 kg/m2

Primary Outcome Measures :
  1. Measures of taste and smell, and eating behavior [ Time Frame: At enrollment ]
    Compare individuals with obesity to healthy controls in measures of taste and smell and eating behaviors.

Secondary Outcome Measures :
  1. Inflammatory markers, exosome and microbiota [ Time Frame: At enrollment ]
    Compare individuals with obesity to healthy controls in measures of inflammation (cytokines and chemokines) in circulating blood, and neuronally-derived exosomes from plasma, and in the oral and nasal microbiome composition and its metabolites.

  2. Gene expression, DNA methylation, taste and smell measures [ Time Frame: At enrollment ]
    Compare individuals with obesity to healthy controls on transcriptomic and epigenomic profiles in monocytes, based on gene expression (RNA sequencing) and whole genome DNA methylation, to identify associated variations in taste and smell perception.

  3. Biological measures, personal factors, taste and smell measures [ Time Frame: At enrollment ]
    Examine how biological measures of inflammation and genomic profiles relate to taste and smell variations based on personal factors (i.e., race, age, and sex) and other factors (i.e., diet) within the obese group

  4. Severity of neuropsychological sysmptoms such as fatigue, anxiety, depression, sleep; perceived stress, pain and QoL [ Time Frame: At enrollment ]
    Evaluate symptoms clusters with alterations in taste and smell and identify phenotypic symptoms characteristics

Information from the National Library of Medicine

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study. To learn more about this study, you or your doctor may contact the study research staff using the contacts provided below. For general information, Learn About Clinical Studies.

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Ages Eligible for Study:   18 Years to 50 Years   (Adult)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   Yes
Sampling Method:   Non-Probability Sample
Study Population
Participants will be recruited from the Washington DC metropolitan area and vicinity.

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 50 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


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 or have used any of the following medications within the 6 months prior to screening: steroidal anti-inflammatory medication, medications known to inhibit taste response (GLP1 agonists), antiepileptic or antidepressant agents, glucocorticoids, antibiotics.
  • Nonsteroidal anti-inflammatory medication within 2 weeks.
  • Received a diagnosis by a medical professional of morbid obesity, liver or renal disease.
  • Individuals with 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 (cigarettes, pipe, etc.), stimulants, cocaine, opioids, or marijuana (by urine drug screen and history/physical exam) in the last 30 days.
  • Currently have an uncontrolled medical disorder (i.e., gastrointestinal, endocrine, cardiac, psychiatric).
  • Any history of chronic rhinitis, eating disorder (including binge eating), acute or chronic upper respiratory infection, allergic rhinitis, nasal polyps, or daily use of nasal sprays.
  • Hemoglobin A1C level > 6.5%.
  • Abnormal complete blood count (CBC): White Blood Cell Count < 4 or > 10 K/uL, Red Blood Cell Count < 4 or > 7 M/uL, Hemoglobin < 13 or > 18 g/dL, Hematocrit < 39 or > 52%
  • Regular users of probiotics/yogurt consumption >= 1 serving per day for the last 30 days.
  • 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).
  • Current cold/flu symptoms
  • Persistent loss of taste and/or smell due to COVID-19
  • 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.

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT04714892

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Contact: Monica S Atkinson (301) 402-8940

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United States, Maryland
National Institutes of Health Clinical Center
Bethesda, Maryland, United States, 20892
Contact: For more information at the NIH Clinical Center contact Office of Patient Recruitment (OPR)    800-411-1222 ext TTY8664111010   
Sponsors and Collaborators
National Institute on Alcohol Abuse and Alcoholism (NIAAA)
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Principal Investigator: Paule V Joseph, C.R.N.P. National Institute on Alcohol Abuse and Alcoholism (NIAAA)
Additional Information:
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Responsible Party: National Institute on Alcohol Abuse and Alcoholism (NIAAA) Identifier: NCT04714892    
Other Study ID Numbers: 10000261
First Posted: January 20, 2021    Key Record Dates
Last Update Posted: July 26, 2021
Last Verified: March 25, 2021

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Studies a U.S. FDA-regulated Drug Product: No
Studies a U.S. FDA-regulated Device Product: No
Keywords provided by National Institutes of Health Clinical Center (CC) ( National Institute on Alcohol Abuse and Alcoholism (NIAAA) ):
Additional relevant MeSH terms:
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Nutrition Disorders
Body Weight