Body composition, physical activity, and quality of life in pediatric patients with inflammatory bowel disease on anti-TNF therapy—an observational follow-up study

Inflammatory bowel diseases (IBD)—Crohn’s disease (CD) and ulcerative colitis (UC)—negatively affect health-related quality of life (HRQoL) and physical activity (PA) and are often associated with undernutrition. Malnutrition encompasses imbalances in energy, protein, and other nutrients that adversely affect function, clinical outcomes, and body form, including losses in fat-free mass (FFM) and skeletal muscle mass (SMM), even in the presence of a normal BMI. Loss of SMM increases risk for sarcopenia, which predicts adverse outcomes in pediatric IBD, including relapse, surgery, and reduced biologic efficacy. PA is associated with HRQoL and BC, positively influencing HRQoL and lean mass in IBD. Elevated TNF-α contributes to skeletal muscle loss and growth impairment. Adult studies suggest anti-TNF therapy may improve sarcopenia by reducing inflammation and catabolism, but pediatric data are limited. Because BC, HRQoL, and PA appear interrelated, and longitudinal changes during biologic therapy have not been evaluated in pediatric IBD (with only one prior cross-sectional study showing lower lean mass, grip strength, and PA vs controls), the primary aim was to assess changes in BC, HRQoL, and PA in children initiating anti-TNF therapy and to compare BC and PA to healthy controls. A secondary aim was to compare baseline characteristics and BC changes in patients with and without risk of sarcopenia at therapy initiation.

Prior research links malnutrition and impaired body composition (including reductions in FFM and SMM) to poorer outcomes and HRQoL in IBD, with sarcopenia associated with higher relapse and surgery risk and reduced biologic efficacy in children. Physical activity has been shown to positively influence HRQoL and lean mass in IBD. Elevated TNF-α is implicated in skeletal muscle loss and growth impairment; adult studies indicate anti-TNF may ameliorate sarcopenia via anti-inflammatory effects, though pediatric evidence is scarce. Only one cross-sectional pediatric study assessing BC, PA, and HRQoL concurrently reported significantly lower lean mass, grip strength, and PA in IBD compared with controls. Data comparing BC deficits by IBD subtype are mixed: CD often shows greater lean mass deficits than UC, though some pediatric studies report no differences, and others suggest FFM reductions in UC with preserved BMI. Overall, literature supports interrelations among BC, PA, and HRQoL and a potential beneficial role of anti-TNF on growth and musculoskeletal parameters, warranting longitudinal evaluation in pediatric cohorts.

Design: Prospective, single-center observational cohort conducted from October 2016 to December 2018 at the 1st Department of Pediatrics, Semmelweis University, Budapest, Hungary. Participants: Pediatric IBD patients aged 10–19 years initiating anti-TNF therapy were consecutively enrolled with informed consent; exclusions included conditions affecting BC, PA, or HRQoL (e.g., autism spectrum disorder, edema, cirrhosis, hypoalbuminemia), hypersensitivity to infliximab or therapy discontinuation, endocrine/chronic disorders (e.g., diabetes mellitus), active malignancy, or lack of consent. Diagnosis followed Porto criteria; anti-TNF indication aligned with Hungarian National Health Insurance and international guidelines. Controls: 307 healthy children (10–18 years) from local schools were recruited to establish population- and device-specific BC reference values; exclusions were recent acute illness and chronic disorders/disabilities. Of these, 204 controls completed PA questionnaires. Measurements and time points: Assessments at start of anti-TNF (M0), end of induction (M2), and 6 months (M6) included anthropometry, BC, HRQoL, PA, disease activity, and laboratory parameters. Anthropometry and BC: Height by stadiometer; BMI calculated as kg/m2. Height, weight, BMI converted to age- and sex-specific Z scores using Hungarian references. BC measured by multifrequency bioelectrical impedance (InBody 720; 5, 50, 250, 500, 1000 kHz) between 8:00–12:00, after ≥2 h fasting, minimal clothing, upper limbs abducted 30°, no jewelry/watches. Extracted FFM, SMM, and body fat mass (BFM). BC Z scores derived using LMS method to generate age-, sex-, and BMI-specific references from the healthy cohort. Physical activity: PAQ-C/PAQ-A 7-day recall (10 items; score 1–5). All patients completed at each time point; 204 controls completed once. Patients’ PA compared to age-, sex-, and BMI-matched controls at 1:3 ratio. HRQoL: IMPACT-III (Hungarian version), six subscales, total score 35–175. Disease activity: Paris classification for phenotype/location; PCDAI for CD and PUCAI for UC. Remission: PCDAI ≤10 (CD); PUCAI <10 (UC). Response: ≥15-point PCDAI reduction (CD); ≥20-point PUCAI reduction (UC). Anti-TNF therapy: Adalimumab or infliximab per standard protocols; four patients required intensification; no discontinuations during study. Statistics: Continuous variables as mean ± SD; Z scores for anthropometrics per national data. LMS method used to build BC references. Independent t tests for baseline group comparisons; GLM to assess longitudinal changes in BC, labs, and disease activity; Pearson correlations as appropriate. Nonparametric analyses for HRQoL and PA (Friedman test; Wilcoxon signed-rank post hoc with Bonferroni correction, p < 0.017; Mann–Whitney U for between-group comparisons). Significance set at p < 0.05. Software: Statistica (LMS) and IBM SPSS v20. Ethics: Approved by Semmelweis University Institutional Committee for Research Ethics (SE TUKEB No: 215/2016).

- Cohort: 32 pediatric IBD patients (21 CD, 11 UC); controls: 307 for BC reference, 204 for PA comparison. Baseline differences between CD and UC included lower hemoglobin (114.0 ± 19.8 vs 129.6 ± 16.6 g/dL, p = 0.03) and higher platelets in CD (451.0 ± 169.4 vs 285.3 ± 120.9 G/L, p = 0.005). Baseline BC: FFM Z score lower in CD than UC (−0.4 ± 1.1 vs 0.5 ± 1.3, p = 0.04); BMI Z similar (CD −1.1 ± 0.7; UC −0.9 ± 0.7). - Longitudinal BC: In CD, FFM Z increased significantly from M0 to M6 (−0.3 ± 1.2 → 0.1 ± 1.2; p < 0.05). No significant BC changes in UC over six months. - Physical activity: CD had lower baseline PA vs matched controls (median 1.1 vs 2.4), but the difference disappeared by M6 (2.3 vs 2.4). UC PA was comparable to controls at baseline and remained stable (M0: 1.6 vs 2.3; M6: 1.8 vs 2.2). - HRQoL: No significant change over time (CD median IMPACT-III: 128.5 at M0 to 144 at M6; UC: 109 to 116). - Correlation: In CD at baseline, IMPACT-III correlated with PA (r = 0.73, p = 0.007). - Disease activity outcomes: At M2, remission in 58% of CD (10/17) and 37.5% of UC (3/8); at M6, active disease persisted in 21% of CD (3/14) and 45% of UC (5/11). - Subgroup (risk of sarcopenia defined as SMM Z ≤ −1): These patients were younger and shorter at baseline than those without risk (age 13.9 ± 2.8 vs 16.4 ± 1.9 years, p < 0.05; lower height Z). SMM Z increased significantly in the at-risk group over time but remained lower than in the non-risk group at M2 and M6; no HRQoL or PA differences between groups.

The study demonstrates that initiating anti-TNF therapy in pediatric CD is associated with a significant increase in fat-free mass within six months, while UC patients, who exhibited fewer baseline BC deficits, did not show BC changes over the same period. The initial PA deficit observed in CD relative to healthy peers normalized by six months, suggesting functional recovery alongside improvements in body composition. These findings support the hypothesized triad relationship between BC, PA, and HRQoL in pediatric IBD and align with mechanistic expectations that TNF-α blockade reduces inflammation-driven catabolism and facilitates musculoskeletal accrual. Despite trends, HRQoL did not significantly improve, potentially reflecting earlier initiation of biologics (higher baseline IMPACT-III, lower disease activity) and the need for longer recovery time to detect changes in patient-reported outcomes. The subgroup analysis highlights that younger patients with lower SMM Z scores are particularly vulnerable but can achieve significant gains in muscle mass under anti-TNF therapy, underscoring the importance of early identification and targeted monitoring. Overall, the results suggest that anti-TNF therapy contributes to improvements in lean mass and normalization of PA in CD, whereas standard anthropometrics (weight/BMI) may miss meaningful changes in nutritional status, reinforcing the value of BC monitoring in pediatric IBD care.

Anti-TNF therapy in pediatric Crohn’s disease was associated with significant increases in FFM Z scores over six months, while BMI and weight remained unchanged, indicating that traditional anthropometrics are insufficiently sensitive for monitoring nutritional recovery. No significant changes were observed in UC body composition, HRQoL, or PA during the study period. Younger patients with lower baseline SMM Z scores (risk of sarcopenia) demonstrated significant improvements in SMM yet remained below peers, highlighting their vulnerability. Clinical care should prioritize routine body composition assessment and encourage physical activity to support functional recovery. Future research should include larger multicenter cohorts, longer follow-up, dietary intake assessment, and functional muscle measures to better characterize the trajectories of BC, PA, and HRQoL under biologic therapy.

- Small sample size and single-center design limit generalizability. - Short follow-up period (six months) may be insufficient to detect changes in HRQoL and sustained PA differences. - Lack of detailed dietary intake data limits interpretation of nutritional contributions to BC changes. - Absence of functional muscle assessments (e.g., grip strength) to complement body composition. - Control PA data were cross-sectional rather than longitudinal.