Changes in olfactory function in children and adolescents with obesity following an inpatient weight loss program: a longitudinal study

BACKGROUND: Obesity is a major global public health burden, yet the mechanisms underlying interindividual variability in treatment response remain poorly understood. Olfactory function influences eating behavior and may differ in individuals with obesity. However, evidence in pediatric populations is limited, and their responsiveness to weight loss remains unclear. This study aimed to assess olfactory function in children and adolescents with obesity before and after an inpatient weight loss intervention. Specifically, we examined whether olfactory performance is within normative values and whether it changes in response to weight reduction. METHODS: Sixty children and adolescents with overweight or obesity (13.0 ± 1.9 years, BMI z-score: 2.5 ± 0.5) underwent a structured inpatient rehabilitation program (mean duration: 38 ± 10 days) integrating nutrition therapy, physical activity, stress management, and behavioral modification. Olfactory function was assessed at baseline (T1, ~ 7 days after admission) and after the intervention (T2, ~ 27 days after T1) using the Sniffin' Sticks Test©, comprising odor threshold, discrimination, and identification. At both time points, participants self-reported their perceived olfactory ability. RESULTS: At T1, data were available for 59 participants; 50 completed the follow-up assessment at T2. Completers showed significant reductions in body weight and BMI z-score (p < .001). Olfactory function at T1 was largely within the normative range when compared with age-matched reference data. During weight loss, olfactory function remained largely stable: odor identification improved modestly (p = .003), whereas odor threshold and discrimination showed no significant changes and were not associated with weight loss. Self-reported olfactory ability showed weak correspondence with objective measures and remained unchanged. CONCLUSIONS: Olfactory function in children and adolescents with obesity was largely within the normative range and showed limited change during short-term inpatient weight loss. These findings suggest that olfactory alterations may not be a primary determinant of short-term treatment response. However, age- and domain-specific variability may still be relevant for how individuals perceive and respond to food-related cues, with potential implications for dietary adherence and long-term weight management. Future studies with normal-weight control groups should examine whether such variability contributes to differences in eating behavior and long-term outcomes. TRIAL REGISTRATION: DRKS00005122.