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.

Study Overview

• Status: Completed
• Conditions: Obesity; Taste Disorders; Smell Disorder
• Intervention / Treatment: Other: Sleeve Gastrectomy (SG) and Roux-en-Y Gastric Bypass (RYGB)

Detailed Description

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.

• Study Type: Observational
• Enrollment (Actual): 101

Contacts and Locations

Study Locations

• Turkey (Türkiye)
  • Capa
    • Istanbul, Capa, Turkey (Türkiye), 34093
      • Istanbul University, Faculty of Medicine, Department of Endocrinology and Metabolism

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Adults aged 18-65 years who have undergone bariatric surgery (Sleeve Gastrectomy or Roux-en-Y Gastric Bypass) at least 3 months prior to enrollment, recruited from patients followed in clinical nutrition and bariatric surgery outpatient clinics.

Description

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

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Sleeve Gastrectomy (SG); Participants who underwent sleeve gastrectomy at least 3 months prior to enrollment.	Other: Sleeve Gastrectomy (SG) and Roux-en-Y Gastric Bypass (RYGB); 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.
Roux-en-Y Gastric Bypass (RYGB); Participants who underwent Roux-en-Y gastric bypass at least 3 months prior to enrollment.	Other: Sleeve Gastrectomy (SG) and Roux-en-Y Gastric Bypass (RYGB); 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.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Power of Food Scale (PFS) Score	Hedonic hunger assessed using the Power of Food Scale (range: 1-5; higher scores indicate greater hedonic hunger).	Baseline (Day 1, at study enrollment)
Modified 33-item Taste and Smell Questionnaire Score	Changes in taste and smell perception assessed using a modified 33-item questionnaire (range: 0-33; higher scores indicate more pronounced sensory changes).	Baseline (≥3 months after bariatric surgery, at study enrollment)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Mediterranean Diet Adherence Screener (MEDAS) Score	Adherence to the Mediterranean diet assessed using the 14-item MEDAS questionnaire (range: 0-14; higher scores indicate greater adherence).	Baseline (≥3 months after bariatric surgery, at study enrollment)
Body Mass Index (BMI)	BMI calculated as weight (kg) / height (m²).	Baseline (Day 1, at study enrollment)
Waist-to-Hip Ratio (WHR)	WHR calculated as waist circumference (cm) / hip circumference (cm).	Baseline (Day 1, at study enrollment)
Energy Intake Adequacy (% of TÜBER-2022 reference)	Daily energy intake adequacy compared to TÜBER-2022 reference values.	Baseline (Day 1, at study enrollment)
Protein Intake Adequacy (% of TÜBER-2022 reference)	Daily protein intake adequacy compared to TÜBER-2022 reference values.	Baseline (Day 1, at study enrollment)
Micronutrient Intake Adequacy (e.g., iron, folate, vitamin E; % of TÜBER-2022 reference)	Micronutrient intake adequacy compared to TÜBER-2022 reference values.	Baseline (Day 1, at study enrollment)
Nutrient Adequacy Score (based on TÜBER-2022 reference values)	Composite score reflecting the percentage adequacy of daily energy, macronutrient, and micronutrient intakes compared to TÜBER-2022 reference values. Higher scores indicate greater adequacy.	Baseline (Day 1, at study enrollment)

Collaborators and Investigators

• Sponsor: Hanife Köksal
• Collaborators: Uskudar University

Study record dates

Study Major Dates

• Study Start (Actual): January 1, 2024
• Primary Completion (Actual): November 30, 2024
• Study Completion (Actual): January 31, 2025

Study Registration Dates

• First Submitted: August 12, 2025
• First Submitted That Met QC Criteria: December 4, 2025
• First Posted (Actual): December 17, 2025

Study Record Updates

• Last Update Posted (Actual): December 17, 2025
• Last Update Submitted That Met QC Criteria: December 4, 2025
• Last Verified: December 1, 2025

More Information

Terms related to this study

• Keywords: Mediterranean Diet; Hedonic Hunger; bariatric surgery outcomes; Nutrient Adequacy; Power of Food Scale (PFS); Taste and Smell Questionnaire; MEDAS
• Additional Relevant MeSH Terms: Neurologic Manifestations; Nervous System Diseases; Nutrition Disorders; Overnutrition; Body Weight; Sensation Disorders; Overweight; Pathological Conditions, Signs and Symptoms; Nutritional and Metabolic Diseases; Signs and Symptoms; Obesity; Olfaction Disorders; Taste Disorders; Therapeutics; Surgical Procedures, Operative; Digestive System Surgical Procedures; Anastomosis, Surgical; Bariatric Surgery; Bariatrics; Obesity Management; Gastroenterostomy; Gastric Bypass
• Other Study ID Numbers: USK-NUTR-HK01

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: No - Individual participant data (IPD) will not be shared due to privacy concerns and lack of prior consent for public data sharing from study participants. Only aggregated results will be available in publications.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No