Infliximab (IFX) is used in active Crohn’s disease for induction and maintenance of remission. There are scanty data on weight gain in IBD-patients under anti-TNF treatment. We investigated changes in weight and blood chemistry in anti-TNF-naïve Crohn’s disease patients during their first course of IFX.
Retrospective analysis of 110 patients (77 men, 33 women) aged 34 years (range 14-73), 54 with luminal and 56 with fistulising disease, given at least 3 infusions of IFX (range 3-11). Data regarding body weight, height, C-reactive protein (CRP), haemoglobin and S-albumin at baseline, before the third infusion, at three months and at 12 months were collected.
At 6 weeks, 65 (59%) increased in weight, 73% and 76% at three and 12 months, respectively. There was an increase in median weight (1.7 kg, IQR = 3.1 kg) and BMI (0.5 kg/m, IQR = 1.2 kg/m) at 6 weeks, which persisted at three and 12 months (all  < .001). There was no difference between men and women. Young patients, patients with underweight or fistulising disease increased most in weight. Disease activity assessed by PGA and SES-CD decreased at all time points ( < .05). Increases in weight and BMI correlated with an increase in serum albumin and a decrease in CRP.
Approximately 60% of Crohn’s disease patients experience weight gain within the first six weeks of infliximab treatment. The weight increment correlates with improvements in inflammatory markers and disease activity. The causes of weight gain may be related to treatment induced metabolic changes and reduced inflammatory burden.

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