Visceral adiposity and inflammatory bowel disease

Background: Rates of obesity are increasing worldwide, as is the incidence of inflammatory bowel disease (IBD). Obesity is now considered an inflammatory state. Visceral adiposity in particular may be associated with a more severe inflammatory phenotype in IBD. Aim: The aim of this review article is to summarise the current literature on the association between visceral adiposity and outcomes in inflammatory bowel disease Methods: To collect relevant articles, PubMed/MEDLINE and Embase searches were performed using Boolean search phrases. Grey literature and manual searches were also performed. Abstracts were selected by two independent reviewers based on pre-determined criteria. Full text articles were reviewed, and data extracted and assessed. Results: One hundred twenty-seven abstracts were obtained through the initial search, with 85 abstracts reviewed and 22 full text articles included. Characteristics are included in Table 1. Most of these were retrospective studies and of moderate or weak quality. Studies suggested visceral fat content is higher in Crohn’s disease than in healthy controls. Visceral adiposity was associated with an increased risk of complex Crohn’s disease phenotype (OR 26.1 95% CI 2–75.4; p = 0.02). Post-operative recurrence was higher in patients with higher visceral fat indices (RR 2.1; CI 1.5–3; p = 0.012). There were conflicting data regarding the effect of visceral adiposity on post-operative complications and the efficacy of medical therapy.Table 1Argeny [24]N = 95Visceral fat area (cm²)Visceral fat index (VFA/m²)Bryant [30]N = 110Visceral adipose tissue (VAT) (cm³)VAT/height index (cm³/m²)Fat mass index (kg/m²)Bryant [13]N = 72Visceral adipose tissue (VAT) (cm³)VAT/height index (cm³/m²)Buning [25]N = 50N = 19 healthy controlsConnolly [26]N = 143Decreased SA and increased visceral/subcutaneous ratio were predictive of post-op complications. (p = 0.02; p < 0.001)Cravo [27]N = 71Smooth muscle area (cm²)Visceral fat area (cm²)Subcutaneous fat area (cm²)B2/B3/surgery — significantly lower muscle attenuation. VFI associated with increased risk of complicated phenotype. (OR 26.1; 95% CI 1–75; p = 0.02)Ding [17]N = 164Visceral fat area (cm²)Higher complication rates in patients with visceral obesity (p < 0.001)Ding [14]N = 106Erhayiem [18]N = 50Feng [28]N = 80Visceral fat area (cm²)Subcutaneous fat area (cm²)No significant difference in VFA between Crohn’s disease cohort and control group. (p = 0.669). ROC analysis: detection of disease based on VFA and MFI: AUC 0.776 Sensitivity 77.5% Specificity 67.5%Hafraoui [16]N = 43Total abdominal fat (cm²)Intra-abdominal fat (cm²)Subcutaneous fat (cm²)Ratio of intra-abdominal:total fat area was significantly higher in patients with Crohn’s vs controls. (p = 0.012)Holt [29]N = 44N = 11 placebo groupLi [31]N = 72Visceral fat area (cm²)Subcutaneous fat area (cm²)Post-op recurrence was more frequent with high VFA values. (p = 0.019) VFA and MFI were independent risk factors for post-operative recurrence. (p = 0.013 and p = 0.028, respectively)High VFA and high MFI were significantly higher in patients with endoscopic activity (p = 0.023)Liu [32]N = 59N = 30 (< 15% increase VFA)Magro [33]N = 78VF was higher in Crohn’s disease group (p = 0.004) compared to controlsParmentier-Decrucq [34]N = 132Shen [35]N = 97VFA and MFI were significantly lower in patients with mucosal healing (post-infliximab). (p < 0.0001) SFA was not significantly differentVFA correlated with CDAI (p < 0.001) and was an independent predictive factor for mucosal healingStidham [15]N = 269Thiberge [36]N = 149SAI and VAI were significantly lower in patients who underwent surgery or who died in 6 months post-CT(p = 0.009 and p < 0.001)VanDerSloot [37]Wei [38]N = 86Yadav [39]N = 97N/A not applicable, VFA visceral fat area, VFI visceral fat index, VAT visceral adipose tissue, VHI visceral adipose tissue to height index, SAT subcutaneous adipose tissue, DXA dual-energy X-ray absorptiometry, CT computer tomography, MRI magnetic resonance imaging, US ultrasound, CDAI Crohn’s disease activity index, HBI Harvey-Bradshaw Index, anti-TNF anti-tumour necrosis factor, SA subcutaneous adiposity, ROC receiver operating curve, AUC area under the curve, MFI mesenteric fat index, SAI subcutaneous adiposity index, PPV positive predictive value Conclusion: Visceral adiposity appears to be increased in Crohn’s disease with some evidence that it is also associated with more complex disease phenotypes. There is also a signal that post-operative recurrence rates are affected by increasing mesenteric adiposity. There is a relative lack of data in UC patients and further high-quality studies are necessary to elucidate the relationship between visceral adiposity and IBD and the implications for patient outcomes.