['Untreated celiac disease is traditionally believed to be associated with malabsorption and underweight. However, studies describing body mass index (BMI) in individuals at the time of diagnosis have shown contradictory results. We investigated the differences in weight, height, and BMI in 12- year-old children with screening-detected celiac disease compared to their healthy peers.', 'In a population-based screening study of 12,632 12-year-old children, blood samples were analyzed for markers of celiac disease. Children with elevated markers were referred for a small bowel biopsy. Weight and height were measured in 239 out of 242 children with screening-detected celiac disease (57.3% girls) and in 12,227 children without celiac disease (48.5% girls). BMI was categorized according to the International Obesity Task Force. Age- and sex-specific cut-off points for underweight, normal weight, and overweight were used.', 'Children with celiac disease weighed less and were shorter than their peers (median weight 45.2 kg, interquartile range (IQR) 40.2-52.2 kg vs. 47.0 kg, IQR 41.1-54.4 kg, respectively, p = 0.01; median height 156.5 cm, IQR 151.0-162.0 cm vs. 157.5 cm, IQR 152.0-163.0 cm, respectively, p = 0.04). In comparing those with celiac disease to their healthy peers, 4.2% vs. 5.2% were underweight, 82.0% vs. 72.8% were normal weight, and 13.8% vs. 21.9% were overweight, respectively. There was no association between being underweight and the risk of having undiagnosed celiac disease (Odds ratio (OR) 1.3, 95% CI 0.7-2.4), but the risk was significantly lower among overweight children (OR 0.56, 95% CI 0.4-0.8). Median BMI was slightly lower among the children with screening-detected celiac disease compared to their healthy peers (18.6 kg/m2, IQR 17.1-19.8 kg/m2 vs. 18.8 kg/m2, IQR 17.2-21.1 kg/m2, respectively, p = 0.05), but most of the celiac disease cases had a normal BMI.'] Is body mass index a reliable tool in predicting celiac disease in children?