To assist healthcare professionals in their efforts to screen for overweight at an early stage, we sought to identify early predictive markers of subsequent overweight. To do this, we established a historical cohort of 1,424 children from the Aquitaine region aged 8–9 years enrolled in third grade, for whom we had prior body composition data collected during school health screenings at ages 3–4 and 5–6. The results show that among the 189 out of 1,424 children (13.9%) in the historical cohort who were overweight according to French standards at the 8–9-year-old checkup, 33.8% were already overweight at 3–4 years of age and 54.1% at 5–6 years of age. The combination of the criterion "being overweight at ages 3–4 or 5–6" with the criterion "an increase in body mass index (BMI) of more than 1 point between ages 3–4 and 5–6" appears to be the best marker for identifying the risk of becoming overweight at ages 8–9, with good sensitivity (75.3%) and good specificity (87.9%). Thus, this study shows that it is possible, as early as age 6, to identify the majority of children at risk of becoming overweight or obese by analyzing changes in BMI between ages 3–4 and 5–6. Furthermore, these results reinforce the importance of offering follow-up and care to children who are already overweight between the ages of 3 and 6. (R.A.)