Introduction - Our objective was to estimate the discrepancies between self-reported and measured anthropometric data in a national sample of adults and to assess the implications for estimating the prevalence of overweight and obesity. Methods - Self-reported and measured anthropometric data were collected from 629 participants in the National Nutrition and Health Survey (ENNS). The mean differences in weight, height, and body mass index (BMI) were tested against zero. The agreement between self-reported and measured data for classification into BMI categories for obesity (BMI ≥ 30 kg/m²) and overweight, including obesity (BMI ≥ 25 kg/m²), was tested. Results - The mean difference between self-reported and measured data was -1.05 kg (SE=0.10, p<10⁻³) for weight, 0.79 cm (SE=0.07, p<10⁻³) for height, and -0.63 kg/m² (SE=0.05, p<10⁻³) for BMI. The prevalence of overweight (including obesity) and obesity differed significantly between self-reported and measured data (43.1% vs. 48.5%; p<10⁻³ for overweight, including obesity; 11.1% vs. 14.9%; p<0.03 for obesity). Conclusion - Our results confirm underreporting of weight and overreporting of height in the general population in France, leading to an underestimation of the prevalence of overweight (including obesity) and obesity. (RA)