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NCT Number: NCT07290075

The Relationship Between Olfactory and Gustatory Senses, Hedonic Hunger, and Diet Quality After Bariatric Surgery

This cross-sectional observational study investigates the association between changes in olfactory and gustatory senses and hedonic hunger among individuals who have undergone bariatric surgery. The study also examines the effects of these sensory changes on diet quality and anthropometric measurements. Participants completed a structured questionnaire including sociodemographic and health information, dietary habits, a modified 33-item taste and smell assessment, the Power of Food Scale (PFS), the Mediterranean Diet Adherence Screener (MEDAS), the International Physical Activity Questionnaire (IPAQ), and anthropometric measurements.

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Key information

Conditions

Obesity Body Weight Nervous System Diseases Neurologic Manifestations Nutrition Disorders Nutritional and Metabolic Diseases Olfaction Disorders Overnutrition Overweight Pathological Conditions, Signs and Symptoms Sensation Disorders Signs and Symptoms Smell Disorder Taste Disorders

Age range

18 year–65 year

Sex eligibility

All sexes

Study type

Observational

Primary location

Istanbul University, Faculty of Medicine, Department of Endocrinology and Metabolism

Istanbul, Capa, 34093, Turkey (Türkiye)

About this study

Obesity is a chronic, multifactorial disease that negatively impacts health and quality of life. Bariatric surgery is an effective treatment option for severe obesity, leading to significant and sustained weight loss as well as improvement in obesity-related comorbidities.

Postoperative changes in taste and smell perception are frequently reported by bariatric patients and may influence food preferences, hedonic hunger, and overall diet quality. These sensory alterations can result from anatomical and hormonal changes after surgery, including altered gut hormone secretion (e.g., PYY, GLP-1, ghrelin) and bile acid metabolism, which affect appetite regulation and reward pathways.

This cross-sectional observational study evaluated adults aged 18-65 years who had undergone sleeve gastrectomy (SG) or Roux-en-Y gastric bypass (RYGB) at least three months prior to enrollment. Data collection included sociodemographic and health information, dietary habits, a modified 33-item taste and smell questionnaire, the Power of Food Scale (PFS) to assess hedonic hunger, the Mediterranean Diet Adherence Screener (MEDAS), the International Physical Activity Questionnaire (IPAQ), and anthropometric measurements. Nutrient intakes were analyzed according to the Türkiye Nutrition Guide (TÜBER-2022) reference values.

The primary objective was to determine the relationship between postoperative taste/smell changes and hedonic hunger. Secondary objectives included assessing the association between sensory perception and Mediterranean diet adherence, anthropometric parameters, and nutrient adequacy by surgery type. Findings from this study may guide the development of personalized nutritional follow-up protocols to improve long-term outcomes in bariatric patients.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Adults aged 18 to 65 years
  • History of bariatric surgery (Sleeve Gastrectomy or Roux-en-Y Gastric Bypass)
  • At least 3 months post-surgery at the time of study enrollment
  • Able and willing to provide informed consent

Exclusion criteria

  • Pregnancy
  • History of neurological disorders affecting taste or smell
  • Active upper respiratory infection at the time of assessment
  • Severe psychiatric disorders that may impair participation

Treatment and study plan

Sleeve Gastrectomy (SG) and Roux-en-Y Gastric Bypass (RYGB)

Other

Participants who have undergone sleeve gastrectomy ≥3 months prior to study enrollment; and Participants who have undergone Roux-en-Y gastric bypass ≥3 months prior to study enrollment.

Primary outcomes

  1. Power of Food Scale (PFS) Score

    Time frame: Baseline (Day 1, at study enrollment)

    Hedonic hunger assessed using the Power of Food Scale (range: 1-5; higher scores indicate greater hedonic hunger).

  2. Modified 33-item Taste and Smell Questionnaire Score

    Time frame: Baseline (≥3 months after bariatric surgery, at study enrollment)

    Changes in taste and smell perception assessed using a modified 33-item questionnaire (range: 0-33; higher scores indicate more pronounced sensory changes).

Secondary outcomes

  1. Mediterranean Diet Adherence Screener (MEDAS) Score

    Time frame: Baseline (≥3 months after bariatric surgery, at study enrollment)

    Adherence to the Mediterranean diet assessed using the 14-item MEDAS questionnaire (range: 0-14; higher scores indicate greater adherence).

  2. Body Mass Index (BMI)

    Time frame: Baseline (Day 1, at study enrollment)

    BMI calculated as weight (kg) / height (m²).

  3. Waist-to-Hip Ratio (WHR)

    Time frame: Baseline (Day 1, at study enrollment)

    WHR calculated as waist circumference (cm) / hip circumference (cm).

  4. Energy Intake Adequacy (% of TÜBER-2022 reference)

    Time frame: Baseline (Day 1, at study enrollment)

    Daily energy intake adequacy compared to TÜBER-2022 reference values.

  5. Protein Intake Adequacy (% of TÜBER-2022 reference)

    Time frame: Baseline (Day 1, at study enrollment)

    Daily protein intake adequacy compared to TÜBER-2022 reference values.

  6. Micronutrient Intake Adequacy (e.g., iron, folate, vitamin E; % of TÜBER-2022 reference)

    Time frame: Baseline (Day 1, at study enrollment)

    Micronutrient intake adequacy compared to TÜBER-2022 reference values.

  7. Nutrient Adequacy Score (based on TÜBER-2022 reference values)

    Time frame: Baseline (Day 1, at study enrollment)

    Composite score reflecting the percentage adequacy of daily energy, macronutrient, and micronutrient intakes compared to TÜBER-2022 reference values. Higher scores indicate greater adequacy.

Sponsors and collaborators

Lead sponsor

Hanife Köksal

Other

Collaborators

  • Uskudar University

Registry information

Important dates

Study start
2024
Primary completion
2024
Study completion
2025
First posted
Dec 17, 2025
Registry last updated
Dec 17, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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