High Prevalence of Muscle Loss Observed in Children with IBD: Study

A recent study published in the Journal of Pediatric Gastroenterology and Nutrition highlighted a critical flaw in how healthcare providers assess the nutritional health of children with inflammatory bowel disease (IBD): body mass index (BMI) may not tell the whole story.

This research analyzed data from 516 newly diagnosed IBD patients between ages 5 and 20 found that over a quarter (26%) had significantly low lean mass, despite only 4% having a low BMI. This mismatch underlined the limitations of BMI that fails to distinguish between fat and lean tissue.

The study from 2014 to 2019, used whole-body dual energy X-ray absorptiometry (DXA) to more accurately assess body composition. Through DXA, the team calculated Appendicular Lean Soft Tissue Mass Index (AppLSTMI) and Fat Mass Index (FMI), converting these into age- and sex-adjusted Z-scores to identify abnormalities.

This study found high prevalence of low lean mass (AppLSTMI Z-score < –2) in the pediatric IBD population, even when BMI Z-scores were in the normal range. This suggests that children with IBD could be at risk for muscle mass deficits without appearing underweight by traditional BMI standards.

Crohn’s disease emerged as a strong predictor of low lean mass. Children diagnosed with Crohn’s were significantly more likely to present with low AppLSTMI, when compared to those with ulcerative colitis. Ethnicity also played a role, where children of Asian descent had nearly four times higher odds of having low lean mass despite normal BMI, while Black children were less likely to exhibit this condition.

Other risk factors included active disease, elevated platelet levels and glucocorticoid (steroid) use. Girls in the study had notably lower fat mass when compared to boys, but FMI (fat mass index) rarely fell below the clinical threshold for concern.

Also, none of the children showed fat mass index Z-scores below –2, suggesting that fat stores may be relatively preserved even when muscle mass is significantly depleted. This finding further reinforces the inadequacy of BMI as a standalone nutritional marker in pediatric IBD.

This detailed analysis revealed that among the 112 children with normal BMI but low lean mass, the strongest associations were again seen with Crohn’s disease and elevated platelets. Overall, this study found that lean mass deficits in children with IBD are common and often hidden behind a “normal” BMI reading.

Source:

Alexander, E., Stein, R., Rudra, S., Albenberg, L., & Zemel, B. (2025). Clinical risk factors for body composition deficits in children with inflammatory bowel disease. Journal of Pediatric Gastroenterology and Nutrition. https://doi.org/10.1002/jpn3.70075