Around one in six Year 6 children in Buckinghamshire are obese
The Royal College of GPs said access to healthy food "should be a right and not a privilege," as a study found children in the most deprived areas of England are more than twice as likely to be obese than those in the least deprived.
Additionally, 14.3% of children were overweight.
That means 31% of Buckinghamshire's youngsters are unhealthily overweight when they finish primary school.
The data comes from the Government's annual National Child Measurement Programme – part of its approach to tackling obesity – which records the height and weight of Year 6 and reception-age children in state-maintained schools across England to monitor obesity trends.
It revealed that 27.5% of 10 and 11-year-old children living in the most deprived areas of England were obese compared to 11.9% of those living in the least deprived areas.
Among reception-age children, 13.3% in the most deprived areas were obese compared to 6% in the least deprived.
Buckinghamshire has one of the lowest proportions of England's most deprived neighbourhoods, according to the Index of Multiple Deprivation – a measure of living conditions based on factors including health.
Professor Rachel Batterham, special adviser on obesity for the Royal College of GPs, said the impact of deprivation on childhood obesity rates nationally is "alarming".
She said: "Access to healthy food should be a right and not a privilege.
"The gap in obesity prevalence between children from the most deprived and least deprived areas is stark and growing.
"It is clear that socio-economic factors such as under-employment or poverty play a key role in driving obesity and poor health, and that a whole-government approach is critical in order to reduce health inequalities and obesity rates."
Across England, obesity prevalence among both reception and Year 6 pupils rose in 2019-20, to 9.9% and 21% respectively.
Caroline Cerny, alliance lead at Obesity Health Alliance, said: “These results are not good news for child health.
“In a year when public health has been propelled to the forefront of politics, we now need action on child health – not just words.
“Taking junk food out of the spotlight through restrictions on marketing and promotions – including the long overdue 9pm watershed on junk food adverts – should be the first step.
“The sooner action is taken, the sooner we can give all children the chance to grow up healthy."