Doctors in England are to get new guidelines telling them how to help patients tackle obesity head on.
One in four adults in England is considered obese
GPs will have to treat obesity as if it were any other medical condition and advise overweight patients to slim under the new government guidelines.
Guidance booklets are being sent to all GPs surgeries from Thursday on how to tackle the issue of weight sensitively.
One in four adults in England is now considered obese, with rates among children having doubled in last decade.
The number of obese men has nearly doubled since 1993 from 13% to 24%, while among women rates increased from 16% to 24% over the same period.
This new role for doctors comes after government redoubled its efforts to improve the quality of school meals and pledged to remove junk food from vending machines.
In an interview with the Times newspaper, Public Health Minister Caroline Flint said: "GPs will help people get started on diet and exercise.
"This does not mean someone has to change their life.
"It's not about people having to go on very detailed diets or a very extreme exercise regime.
"It is not about doctors and ministers telling people what to do.
"But it is providing support and finding ways to reach people who need help.
"An obese child has nearly always got obese parents."
But doctors will also be warned to tread carefully, providing parents with gentle prompts to encourage discussion about their child's weight, for example.
They will also encourage families to join a leisure centre and for children to have at least 60 minutes of exercise a day.
GPs will be advised to use the body mass index, where the person's weight in kilograms is divided by his height squared in metres, to get a reading.
Anyone with a result between 25 and 29.9 is considered overweight. A result over 30 gains them an obese label.
Doctors' leaders have been calling for tough action on obesity for some time.
In June last year, a British Medical Association report called for a junk food advertising ban and rules governing the nutritional balance of school meals and pre-prepared food.
The BMA said it had not yet seen the guidelines but added that discussions about a patient's weight was all part of the consultation process anyway.
The Department of Health will make an announcement on the issue on Thursday.