Action is needed to cut the number of north Wales children who are overweight or obese when they start primary school, a report has warned.
More than a quarter of four and five year olds in the region are in the category.
Betsi Cadwaladr health board has drawn up a three-year plan, including helping pregnant women to manage their weight.
But a health expert said being overweight was becoming a "social norm".
Just over 28.6% of four and five year olds in the region are overweight, including 12% who are obese, according to a report to be considered by the board on Thursday.
The report, "Children's health and wellbeing: The impact across the life course", said this was a problem which continued into adulthood in a "vast majority" of cases.
It warned: "Obesity in childhood leads to significant health issues across the life course, and some areas of north Wales have the highest prevalence of childhood obesity in the UK."
The report also found "considerable gaps in north Wales in obesity services to support children and families".
Across Wales, the Child Measurement Programme, published in August 2016, found 26% of reception-aged children were classed as overweight or obese.
Sioned Quirke, an obesity specialist and spokeswoman for British Dietetic Association Wales, said: "Published figures every year are showing an increase [in overall obesity].
"We are not even at the stage where they are levelling out.
"That's not surprising taking into account the type of patients we are seeing every day and the numbers being referred to us. The numbers are increasing every year."