NICE wants GPs to identify when to raise weight management with a patient and then to do it "confidently, but with empathy".
The guidance says doctors need to understand why many adults have difficulty managing their weight and the impact it is having on their lives.
Referrals to NHS, private or voluntary lifestyle weight management programmes will be encouraged, as well as more exercise and behaviour changes.
NICE says weight loss plans need to be based on firm evidence and focus on long-term goals.
In a statement, Professor Mike Kelly, director of the Centre for Public Health at NICE says: "Levels of obesity in England are rising, with a little over a quarter of adults classified as obese and a further 41% of men and 33% of women overweight. This is a huge proportion of our population.
"This draft guidance isn’t about quick fixes, it is about ensuring lifestyle weight management services support people in the long term. Programmes that address diet, activity and behaviour change can help people who are obese lose weight but they are only cost effective if the weight is kept off."
Tam Fry of the Child Growth Foundation and National Obesity Forum will be involved in NICE's consultations over the guidance.
"GPs at the moment have very little training in how to approach the job of explaining weight to the patients themselves and the parents of children who are overweight. They are very reticent to do so without training."
Tam Fry sits on the Royal College of GPs Nutrition Committee and says weight problems are seen as a very delicate issue. "If you don’t have the training, the chances are you are going to exacerbate the situation.
"What NICE is saying is that it's got to be done in the right tone, in the right manner."
So what is the right approach for talking about weight loss with an obese patient? "Before you get tough, you've got to get them on your side.
"You need to empathise with their problem," he says. "But there is a time where the toughness has to come in, to explain very reasonably, what the consequences of being obese are."
If you explain the health risks linked to obesity, "then you are empowering the patients to make up their minds for themselves, rather than being lectured to," he says.
He says the conversations with obese patients can be tricky: "Sometimes they're in denial, they don’t see themselves as being overweight."
Tam Fry says the next challenge for the NHS is making sure there are experts to give healthy eating and weight loss advice. "There are just not enough dietitians to go around in the NHS."
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