Objective To evaluate the impact of anti-TNF-α therapy on nutritional status and dietary intake of inflammatory bowel disease (IBD) patients by measuring body composition using bioelectrical impedance analysis. Methods From October 2013 to October 2014, 40 IBD patients who met the inclusion criteria were recruited in Guangzhou Red Cross Hospital and Shenzhen People’s Hospital, including 33 Crohn’s disease patients and 7 ulcerative colitis patients. All patients were treated with anti-TNF-α therapy, of which 24 patients received Adalimumab therapy and 16 patients received Inf?liximab therapy for 12 weeks. Body composition of all patients was tested by Inbody 720 Body Composition Analyzer before and after treatment. Related parameters including body weight, body mass index (BMI), fat-free mass index (FFMI), body fat mass index (BFMI), body fat percentage, visceral fat area, skeletal muscle mass index (SMI) and body cell mass (BCM) were recorded. The differences of body composition changes were compared between the two groups. The nutritional intake of the patients before and after treatment were calculated by Nutricomp Diet Cad? software and compared. Results BMI and muscle parameter after treatment were significantly increased compared with those before treatment (P < 0.05), while the fat parameters did not change significantly (P > 0.05). There was no significant difference in body composition between the Adalimumab treatment group and the Infliximab treatment group (P > 0.05). For nutritional intake analysis, IBD patient’s energy intake and major nutrient (protein, carbohydrate and fat) intake after anti-TNF-α therapy were significantly increased after treatment compared with those before treatment (P < 0.05). Conclusions Anti-TNF-α therapy can significantly increase the body weight and muscle related index in the patients with IBD, without increasing fat parameters, leading to a favorable change in the patients' body, increasing the dietary intake and improving their nutritional status. In addition, the impact of Infl iximab and Adalimumab therapy on body composition has no significant difference.