The Scottish Health Survey revealed 15% of children were obese and a further 13% were overweight.
A charity is calling for urgent action to tackle obesity as figures showed one in seven children in Scotland is dangerously overweight.
Cancer Research UK called for a sugar tax and checks on junk food advertising as the Scottish Health Survey revealed 15% of children were obese and a further 13% were too heavy.
Children with a parent who is obese were found to be significantly more at risk of being overweight, with just 58% of young people in this category having a healthy body mass index.
The study also found that only 12% of children aged 2-15 ate the recommended five daily portions of fruit and vegetables.
The number of children who are overweight or obese in Scotland is shocking. This is a huge worry for the health of the nation
Professor Linda Bauld, Cancer Research UK's cancer prevention expert based at the University of Stirling, said: “The number of children who are overweight or obese in Scotland is shocking. This is a huge worry for the health of the nation.
“If left unchecked, obesity will lead to a rising tide in ill-health, including cancers, and become a crippling burden on the NHS. The Scottish Government must take steps to protect youngsters from being bombarded by junk food marketing on TV, as well as the barrage of supermarket multi-buy offers on sugar and fat-laden food and drinks.
“Scots have a bigger thirst for fizzy drinks than anywhere else in the UK and so we need to see the benefits of the promised tax on sugary drinks as soon as possible.
“We want to help give children the best start in life and reduce their risk of developing cancer in their lifetime. Measures to help us enjoy a better diet can make it easier for us all to stack the odds of not getting cancer in our favour.”
According to the study, 36% of Scottish adults aged 16 and over were overweight, and 29% were obese.
Public health minister Aileen Campbell said the Scottish Government was committed to improving the nation’s health.
She said: “I recognise we have much more work to do to improve Scotland's public health. Many of these indicators are static, or not improving as quickly as we want.
"This government is committed to bringing forward new strategies for obesity, mental health, oral health and alcohol. We also remain committed to introducing minimum unit pricing to tackle the damage which high strength low cost alcohol causes in our communities."
The annual report into Scotland’s health surveyed 5000 adults and 1,421 children in 2015.
Among its other findings was that the number of children being exposed to second-hand smoke in their homes had fallen from 11% to 6%. Adult smoking also saw a small drop, figures showed.
Sheila Duffy, chief executive of anti-smoking charity Ash Scotland, said: “This is a significant drop, and good news for the Scottish Government’s target of halving children’s exposure to second-hand smoke by 2020.
“Tens of thousands more children are now protected from breathing dangerous tobacco smoke in Scotland’s homes.”
