Young children being overweight is increasing worldwide. The World Health Organization estimated that 35 million children under 5 were overweight in 2024. In France, before age 6, the most useful monitoring indicator is not weight alone. It is the shape of the body mass index curve, particularly the timing of the adiposity rebound.
This article brings together the figures available from official institutions, explains what this rebound is, and details the risk factors identified during the early years. No data has been extrapolated.
Young children being overweight: what do the figures show?
Three sets of data are authoritative.
WHO global data
According to the World Health Organization, 35 million children under 5 were overweight in 2024. The increase is particularly pronounced in Africa.
Among 5- to 19-year-olds, the prevalence of overweight rose from 8% in 1990 to 20% in 2022. More than 390 million children and adolescents were affected at that time.
The shift documented by UNICEF
In a report published on September 10, 2025, UNICEF described an unprecedented threshold. Among 5- to 19-year-olds, obesity now affects 9.4% of children, compared with 9.2% for underweight.
This is the first time worldwide that obesity has surpassed thinness as the dominant form of malnutrition in this age group. The report puts the number of children and adolescents living with obesity at 188 million, and the number who are overweight at 391 million.
The situation in France
The French National Authority for Health indicates that 17% of children and adolescents aged 6 to 17 are overweight, including obesity. Among them, 4% are living with obesity.
One limitation must be made clear: in France, there is no prevalence measurement that is equally robust for children under 3. Published figures concern older age groups. This is precisely why monitoring an individual curve matters more than comparing it with an average.
What is the adiposity rebound?
A child's body mass index curve is not linear. It rises sharply during the first year, then falls. It subsequently rises again: this low point followed by a rise is called the adiposity rebound.
The French National Authority for Health care pathway guide places this rebound at around 5 to 6 years of age during typical development. A rebound occurring before age 3 is considered early.
The rule stated by the French National Authority for Health is straightforward: the earlier the rebound, the higher the risk of developing obesity. This signal appears on the curve well before the child's weight looks abnormal to the eye.
How to interpret it in practice
Body mass index is calculated by dividing weight in kilograms by height in meters squared. This figure is plotted on the health record curve, adapted to age and sex.
The thresholds used are those of the International Obesity Task Force. Overweight corresponds to a BMI between the IOTF 25 and 30 thresholds. Obesity corresponds to a BMI above the IOTF 30 threshold.
What matters is not an isolated point, but the trajectory. A curve that rises early and consistently warrants medical advice, even if each individual measurement remains within the normal range.
How often should measurements be taken?
The French National Authority for Health reminds us that weight, height, and BMI calculation are part of every clinical examination. In practice, every follow-up appointment is an opportunity to plot the point.
After age 6, an annual check is considered sufficient in the absence of risk factors. When risk factors are present, a check every six months is recommended from age 3.
What are the risk factors from the first months?
The French National Authority for Health guide identifies several perinatal factors associated with an increased risk. They are useful to know about, but should never become a source of guilt.
- Maternal overweight or obesity before pregnancy.
- Excessive gestational weight gain.
- Gestational diabetes or type 2 diabetes in the mother.
- Maternal smoking.
These factors increase a probability. They do not determine an outcome. A child with several of these factors may follow a perfectly regular curve.
What the WHO recommends for the early years
Prevention recommendations for early childhood are few and stable over time.
Nutrition
The WHO recommends exclusive breastfeeding for the first six months, followed by continued breastfeeding until 24 months or beyond, alongside appropriate complementary foods. Our article on breastfeeding provides details on the recommendations and available resources.
Reducing sugary drinks and energy-dense foods is the second measure mentioned. French guidelines for starting solid foods are covered in our article on complementary feeding according to ANSES.
Movement and screens
The WHO recommends limiting the time young children spend inactive and the time they spend in front of screens. Its physical activity guidelines for children under 5 are detailed in our article on physical activity recommendations.
For an infant, physical activity does not mean playing sports. It means spending time freely on the floor several times a day. This is why a floor play space matters more than an additional piece of equipment.
A clear, insulating, shock-absorbing surface, such as a foldable, reversible play mat, makes this free time possible without constraints. By contrast, time spent in bouncers, playpens, or seats quickly adds up. Our article on motor skills mats explains how to organize this activity according to age.
For screens, the available data and current recommendations are compiled in our article on screen time before age 3.
What to remember, and what not to conclude
Being overweight in young children is a worldwide phenomenon that is measured and increasing. The most robust French figures concern 6- to 17-year-olds, not very young children.
For a child under 3, the relevant monitoring is individual: a body mass index curve plotted at every appointment, with attention paid to the timing of the rebound. A rebound before age 3 warrants medical advice, not a diet.
No dietary restriction should be introduced for a young child without a doctor. Growth and brain development require high energy intake during this period.
Sources
- World Health Organization, Obesity and overweight, fact sheet, 2024 data for children under 5 and 2022 data for 5- to 19-year-olds.
- UNICEF, report on child nutrition, September 10, 2025.
- French National Authority for Health, Care pathway guide: overweight and obesity in children and adolescents, 2022, updated in 2023.
- French National Authority for Health, Overweight and obesity in children and adults: what care pathway?, February 28, 2024.
