More than 12% of children in Wales are classed as obese, with nearly 30% of five year olds classed as overweight.
Research published by Public Health Wales shows that during 2011/12, 71% of children aged four or five were classified as healthy on the body mass index (BMI).
The number of overweight and obese children in Wales (28%) is higher than in England (23%).
Dr Ciarán Humphreys, consultant in public health for Public Health Wales said, “This is the first time we have had a clear picture of the how children in Wales are growing and although the headline figures are worrying, this is something that can be reversed.
“We must have a response from all sectors in society including health, education and local communities themselves to ensure our children are able to adopt healthy lifestyles. This can be anything from making our communities more pedestrian and bicycle friendly to reducing access to unhealthy fast food near schools.”
The findings are from the first report based on the Child Measurement Programme, which collected information on the heights and weights of 29,400 reception age children in Wales during the 2011/12 school year.
Dr Ruth Hussey, Chief Medical Officer for Wales, said; “I welcome this first report on the growth of children at school entry across Wales. Having good information is the basis for effective action on healthy child growth and to reduce childhood obesity.
“This report provides a baseline from which we can monitor our progress as a nation and more locally, into the future. Together, we must work for a healthy, active and resilient community in Wales where all children have the best start in life.”