Obesity, a common health condition in adolescence leading to severe medical complications, is assumed to be influenced by temperament factors. This paper investigates associations between reactive and regulative temperament, problematic eating behaviours and excess weight. Several self‐report instruments were completed by 130 adolescents (mean age 14.13 ± 0.61 years), including 27 overweight and obese individuals (20.8%). Bootstrap analysis revealed a mediating effect of restrained eating on the relation between reactive temperament and body mass index percentile, which differed according to gender: Restrained eating, which predicted weight gain, was more present in girls having a higher sensitivity to reward and in boys showing a higher sensitivity to punishment. No effect of regulative temperament was found. These results have important implications for weight management programmes, as they suggest that reducing restrained eating by working on temperament may help to control weight. Copyright © 2015 John Wiley & Sons, Ltd and Eating Disorders Association.