Risk of obesity during a gluten-free diet in pediatric and adult patients with celiac disease: a systematic review with meta-analysis

Context: Obesity is a significant risk factor for many pathological conditions. Whether a gluten-free diet (GFD) is a risk factor for overweight or obesity remains controversial. Objective: The primary aim of this study was to assess the prevalence of body mass index (BMI) categories at disease presentation and the variation in BMI category from underweight/normal to overweight/obese and vice versa during a GFD. Data sources: PubMed, Scopus, and Web of Science databases were searched through February 2021 for retrospective, cross-sectional, and prospective studies reporting BMI categories at disease diagnosis and during a GFD. Data extraction: Data were extracted by 2 reviewers independently. Disagreements were resolved by consensus; a third reviewer was consulted, if necessary. Risk of bias was assessed with the Cochrane ROBINS-I tool. Data analysis: Subgroup analysis based on age (pediatric/adult patients), study design (prospective, cross-sectional, retrospective), and duration of GFD was performed.. Forty-five studies were selected (7959 patients with celiac disease and 20 524 healthy controls). The mean BMI of celiac patients at presentation was significantly lower than that of controls (P < 0.001). During a GFD, the mean BMI increased significantly (mean difference = 1.14 kg/m2 [95%CI, 0.68-1.60 kg/m2]; I2 = 82.8%; P < 0.001), but only 9% of patients (95%CI, 7%-12%; I2 = 80.0%) changed from the underweight/normal BMI category to the overweight/obese category, while 20% (95%CI, 11%-29%; I2 = 85.8%) moved into a lower BMI category. Conclusion: Most celiac patients had a normal BMI at presentation, although the mean BMI was significantly lower than that of controls. A GFD does not increase the risk of becoming overweight/obese, especially in children. The quality of several studies was suboptimal, with moderate or high overall risk of bias and heterogeneity.