The BMA said a generation of children could have chronic health problems
Childhood obesity rates are worryingly high and not being tackled by the Scottish Government's action plan, the British Medical Association has said.
The BMA said one in five primary one pupils were categorised as overweight in 2006-07, while 8.5% and 4.3% were classed as obese and severely obese.
The issue will be raised in parliament later but the BMA has outlined a five-point plan to combat the problem.
Ministers said NHS boards will be given £19m over three years to help children.
The BMA said the Scottish Government's action plan provided little detail on measures that would reverse the trend.
It recommended that ministers focus on five areas - nutrition in schools; exercise; the media and advertising; food labelling and health claims and the role of health professionals.
Dr Dean Marshall, chair of the BMA's Scottish General Practitioners committee, said: "Childhood obesity rates in Scotland are worryingly high.
"It is time for the government to take tough action."
The highest levels of overweight, obese and severely obese children were found in the most deprived areas.
"We are in danger of raising a generation of children burdened with long term chronic health conditions," Dr Marshall said.
"Doctors have a role to play in supporting overweight patients and talking about the dangers of obesity but there is a limit to what they can do."
The Scottish Government published an action plan earlier this year to improve diet, increase physical activity and tackle obesity, called Healthy Eating, Active Living.
It was backed by £56m, of which £40m was new money.
A spokeswoman said health boards around the country would be allocated £19m, to be targeted at helping children over the next three years.
Public Health Minister Shona Robison said: "We are determined to stop the problem of obesity in its tracks, by supporting new mums, babies and all young people to develop healthy eating and active living habits that last a lifetime.
"We are fulfilling our commitment to provide free fruit to mothers and pre-school children but we're going much further than that.
"These new resources will help bring about a wide range of initiatives that support a healthy diet and physical activity."
The BMA said more than 40 people are diagnosed with diabetes in Scotland every day and most of these cases are Type 2 diabetes, which is closely linked with obesity.
The NHS spends at least £2bn in the UK every year on treating ill health caused by poor diet.