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Associate Professor of Medicine
Medical Director, OSU Inflammatory Bowel Disease Center
Abercrombie & Fitch Endowed Chair in Inflammatory Bowel Disease
Division of Gastroenterology, Hepatology and Nutrition
The Ohio State University Wexner Medical Center
Anita Afzali, MD, MPH, FACG, has disclosed that she has received consulting fees from AbbVie, Bristol-Myers Squibb/Celgene, Gilead Sciences, Janssen, Lilly, Pfizer, and Takeda.
The 2021 Crohn’s & Colitis Congress provided interesting data on the relationship between visceral adipose tissue (VAT) and outcomes for patients with inflammatory bowel disease (IBD) and the management of IBD with diet. I applaud the Congress for navigating through the pandemic and providing a variety of abstracts and presentations while including more basic and translational presentations and involving patients and patient advocates on speaking panels and on the organizing committee.
Metabolic syndrome is an area of growing interest in IBD. Although we previously thought of the ”typical” patient with IBD as malnourished and underweight, approximately 20% to 40% of adult patients with IBD are overweight and 15% to 40% are obese. Body mass index (BMI) has traditionally been used to evaluate metabolic status, but measurement of VAT is emerging as a more accurate tool to assess risk for patients with IBD.
VAT Influences Anti‑TNF Treatment Response in IBD
Two abstracts at the 2021 Crohn’s & Colitis Congress focused on the influence of adiposity on anti–tumor necrosis factor (TNF) treatment response and on the need for surgery in adult patients with IBD.
In an abstract on VAT, Gu and colleagues presented data on 182 patients whose VAT volumes were measured by CT scan prior to anti-TNF therapy. The relationship between VAT and anti-TNF treatment response was evaluated after 6 and 12 months. Patients were categorized as having low, intermediate, and high VAT for analysis. The primary outcome was corticosteroid-free response (CFR), defined as achieving ≥ 1 of the following: a clinical response, endoscopic improvement, and/or 50% normalization of C-reactive protein or fecal calprotectin. The impact of VAT on IBD-related surgery was also assessed.
The authors found that VAT volume was not associated with CFR at 6 months, but patients with intermediate VAT volumes had increased CFR at 12 months vs patients with the lowest volumes. Patients with the highest VAT volumes were significantly more likely to undergo surgery within 6 months than patients with the lowest VAT volumes, but this was not significant at 12 months.
In another abstract, on the visceral fat index (VFI), Gu and colleagues presented data on 181 patients whose VAT and subcutaneous adipose tissue (SAT) were measured to determine their VFI (the ratio of VAT to SAT). The relationships between VFI and anti-TNF treatment response were evaluated after 6 and 12 months. Patients were categorized as having low, intermediate, and high VFI for analysis. VFI was not associated with CFR at 6 or 12 months, but patients with a high VFI were significantly more likely to undergo surgery within 6 and 12 months compared with patients with the lowest VFI.
These results suggest that higher VAT volumes and VFI are associated with more aggressive disease and/or reduced responsiveness to anti-TNF therapy. This may be a call to action for increased efforts for healthy eating, diet, exercise, and weight loss to try to help patients reduce VAT and VFI. I think VFI and VAT are helpful assessment tools—and perhaps more accurate than BMI alone. We should remember that there are multiple anti-TNF therapeutics, and the route of administration (infusion vs subcutaneous) can affect drug bioavailability and treatment response. Previous studies have shown that anti-TNF therapy administered subcutaneously has a lower response in patients with higher BMIs, and infusions are weight-based formulations for this purpose. So it is important to determine whether the associations among VAT, VFI, and response differ based on the particular anti-TNF therapy and route of administration. We should also determine whether VAT and VFI affect the response to non‑TNF therapies and better understand the impact on mucosal healing and endoscopic improvement, as well as the influence of microbial factors.
Although we do not routinely calculate VAT, I think it is a better way to evaluate patient risk than BMI. After we better understand the association between VAT or VFI and our current therapies, VAT could be used at diagnosis to determine which patients are more likely to be nonresponders to anti-TNF therapy or at a higher risk for surgery, allowing for earlier, proactive discussion about management strategies individualized for each patient with IBD.
We already know that some diets are proinflammatory and others are anti‑inflammatory and may improve disease response in IBD. The specific carbohydrate diet (SCD) is of particular interest in managing Crohn disease symptoms, and I have had several patients who swear by it, even though it is a very restrictive diet. The Mediterranean diet is also less inflammatory and is of interest in IBD based on findings in other disease states.
The DINE‑CD study by Lewis and colleagues was reported via an oral presentation at the virtual Congress. The study enrolled 194 adult patients with a short Crohn disease activity index (sCDAI) score of 176-399 who were on a stable dose of medication; patients remained on their current therapies during the study, something unique for a diet study in this population. Randomization was to the SCD or the Mediterranean diet, and meals following these diets were delivered directly to patients’ homes. Symptomatic remission (sCDAI < 150 in the absence of initiation or increase of medications), clinical remission (CDAI < 150), and inflammatory response (reduction in fecal calprotectin and C-reactive protein levels) were evaluated in patients after 6 and 12 weeks.
Neither diet was superior in terms of symptomatic remission or clinical remission, which both occurred in slightly more than 40% of patients. In addition, neither diet resulted in the normalization of inflammatory markers, which was disappointing. If we had seen improvement in these markers, it would have suggested that diet promotes additional healing of the mucosa or improved therapeutic response. At the same time, only a small fraction of the patients had their fecal calprotectin and C-reactive protein assessed (13-37 per group), which limits our ability to interpret these data.
As I mentioned above, DINE-CD was unique in that it was done in adult patients and as a supplement to current therapy rather than therapy replacement. Also unique was the increased control over diet by sending food directly to patients’ homes. Diet studies are difficult to conduct and evaluate since you assume that patients are eating the appropriate food and nothing else, so providing the food should have helped with adherence. Additional research should evaluate easy-to-follow diets like the Mediterranean diet in a larger number of patients with Crohn disease. We should also evaluate how changes in diet affect the microbiome due to the significant relationship among diet, disease, and the microbiome.
The take-home message from DINE-CD is that a diet that is easy to follow—like the Mediterranean diet—helps patients to control their disease and improve symptoms while remaining on therapy. We are frequently asked which diets can help patients manage their Crohn disease, and the Mediterranean diet appears to be a healthy option.
Do you currently recommend the SCD or the Mediterranean diet to your patients with Crohn disease? Share your thoughts in the comments section below.