After an increase in the prevalence of overweight (including obesity) among children in France up until 2000, the rate had since stabilized. The third edition of the study on the body weight of second- and third-grade students allows us to track changes in these prevalence rates over the period. The three studies, conducted in 2000, 2007, and 2016 using a similar protocol, involved students aged 7 to 9 years old in CE1 and CE2 grades at schools randomly selected across mainland France. The students’ weight and height were measured by nursing staff from the French Ministry of Education. A self-administered questionnaire completed by parents was used to collect information on the children’s characteristics. In 2016, according to the International Obesity Task Force’s thresholds, 18.7% of girls and 14.4% of boys were overweight (including obese), with the gap between girls and boys being significant for the first time compared to the previous results from 2000 and 2007. The prevalence of obesity was also significantly higher among girls (5.2%) than among boys (3.2%). The stabilization of overweight (including obesity) was confirmed among girls (21% in 2007), while a significant decline was observed among boys (18% in 2007). Among girls, the prevalence of overall thinness increased significantly, rising from 9.5% in 2007 to 13.7% in 2016. These trends will need to be confirmed by further studies and analyzed in greater detail to understand the reasons behind these gender-specific changes.