Effects of body mass index on gastric motility: Comparing children with functional abdominal pain disorders and healthy controls.

Background: Overweight children exhibit a higher prevalence of functional gastrointestinal disorders compared with their normal-weight peers, yet the underlying reasons remain unclear. Gastrointestinal motility, a key pathophysiological factor in functional gastrointestinal disorders, may be influenced by body mass index (BMI).

Aim: To evaluate the impact of BMI on gastric motility parameters in children with functional abdominal pain disorders (FAPDs).

Methods: We assessed gastric motility in 176 children with FAPDs (61.4% females, mean age 7.94 years, SD 1.96 years) and 63 healthy controls (57.1% females, mean age 9.17 years, SD 1.90 years) at the Gastroenterology Research Laboratory, University of Kelaniya, Sri Lanka. FAPDs were diagnosed and subtyped using the Rome IV criteria: Functional abdominal pain 97 patients; irritable bowel syndrome 39 patients, functional dyspepsia (FD) 25 patients; and abdominal migraine 15 patients. Gastric motility was measured using a validated ultrasound method. Weight and height were measured using sensitive standard scales.

Results: The BMIs of children with FAPDs and controls were 15.04 and 15.46 kg/m², respectively (P = 0.33). Fasting antral area (FAA) and antral area at 1 min (AA1) and 15 min (AA15) were significantly greater in patients with FAPD with a higher BMI (2.71 cm², 12.57 cm², and 7.19 cm², respectively) compared with those with a lower BMI (2.12 cm², 10.68 cm², and 6.13 cm², respectively) (P < 0.01). BMI positively correlated with FAA and AA15 (r = 0.18 and r = 0.19, respectively) (P < 0.01) in those with FAPDs. In controls, only AA1 was greater in the higher BMI group (12.51 cm² vs 9.93 cm²) and had a positive correlation (r = 0.33) (P ≤ 0.01). Subgroup analysis revealed that in patients with FD, BMI negatively correlated with gastric emptying rate (GER) (r = -0.59) and antral motility index (MI) (r = -0.49), while in functional abdominal pain, MI positively correlated (r = 0.25) with BMI (P ≤ 0.01).

Conclusion: In children with FAPDs, higher BMI was associated with increased gastric antral distention during fasting and postprandial periods (as indicated by FAA, AA1, and AA15) but not with contractility and transit (MI, GER). However, in the FD subgroup, high BMI correlated with reduced GER and MI. This indicates the possible role of BMI in gastric hypomotility and the pathophysiology of FD. These findings underscore the importance of lifestyle and dietary interventions aimed at optimizing BMI in the management of FAPDs, particularly FD.