Population studies indicate a strong relationship between birth weight (BW) and body size in later life. However, BW as a variable was never accounted for in studies on the relationship between attention-deficit/hyperactivity disorder (ADHD) and overweight. This study aims to assess the relationship between ADHD and overweight with control of birth weight and other confounding factors. Prevalence of overweight was compared in clinical sample of 219 boys with ADHD and 396 boys without ADHD, aged 6–18 years. The following factors were controlled: BW, parents income and education level, place of residence, ADHD type, selected comorbid disorders and stimulant treatment. Overweight and obesity were diagnosed according to the criteria proposed by the International Obesity Task Force. Logistic regression analysis was used to estimate the association between ADHD and the prevalence of overweight and obesity. Boys with ADHD differed significantly from the control group in distribution of low BW (8.2 vs. 3.0 %, χ ² = 8.23, p = 0.02). Low BW was associated with a lower prevalence of overweight than normal and high BW (0 vs. 12.14 %, χ ² = 4.12, p = 0.04). Overweight was observed significantly more often in boys with ADHD (17.3 vs. 8.3 %, χ ² = 11.23, p < 0.001) even after adjustment for BW and other variables (OR = 2.44, 95 % CI 1.38–4.29, p = 0.002) and after controlling for ADHD type, stimulant treatment and selected comorbid disorders. Independently to applied analysis, obesity was not associated with ADHD. Lower birth weight is over twice more often observed in boys with ADHD than in control group. Although this phenomenon may reduce the rate of overweight in the studied group, ADHD remains strongly associated with increased prevalence of overweight.

Objective: Assessment of the prevalence of overweight and obesity in children and adolescents with ADHD with emphasis on pharmacological treatment and comorbid disorders. Method: We analyzed 408 medical records of patients with ADHD aged 7 to 18. Results: The prevalence of overweight (14.71% vs. 12.83%, χ² = 3,586.43, p < .001) and obesity (6.37% vs. 3.45%, χ² = 3,588.19, p < .001) was significantly higher in children with ADHD compared with the population. There was significantly higher incidence of obesity in patients with comorbid diagnosis of adjustment disorder (22.22% vs. 4.42%, χ² = 5.66, p = .02) and mental retardation (19.05% vs. 4.42%, χ² = 7.63, p = .005). Pharmacological treatment was associated with a higher incidence of obesity (8.37% vs. 2.76%, χ² = 4.92, p = .03). Conclusion: Standardized body mass index (BMI), prevalence of overweight, and obesity was higher in patients with ADHD compared with the population. Higher incidence of obesity was shown in patients with analyzed comorbidities.