Doctors should not blame patients for being fat, according to new NHS guidance.
The tone used to discuss obesity should be "respectful" and "non-blaming" in order to "minimise harm".
The National Institute for Health and Care Excellence (Nice) published new draft guidance on tackling obesity, which is subject to consultation.
It said doctors, GPs and other health workers, as well as providers of lifestyle weight management services, should monitor their tone.
The guidance also provides instructions for Public Health England, which is responsible for public health campaigns.
The guidance said all these professionals should "be aware of the effort needed to lose weight and avoid further weight gain and the stigma adults who are overweight or obese may feel or experience".
"Ensure the tone and content of all communications or dialogue is respectful and non-blaming," it stated.
"The terminology used to describe the person's condition should respect individual preferences."
Other recommendations include ensuring equipment and facilities meet the needs of adults who are overweight or obese.
"For example, referrers to, and providers of, lifestyle weight management services should ensure large blood pressure cuffs are available and any new scales can accurately weigh the heaviest patients seen by the service."
GPs and those running weight management programmes for the NHS should also ensure patients have a realistic view of what to expect when losing weight, the guidance continued.
And it should be explained to people who were considering such a programme "how much motivation and commitment is needed to lose weight and maintain weight loss".
Furthermore, they should be told that "no programme holds the 'magic bullet' (that is, no programme can guarantee success)".
Stress should be put on the "importance of making gradual, long-term changes to their eating habits and physical activity and how much weight they might realistically expect to lose in total and on a weekly basis if they adhere to the programme".
The guidance said only people with a body mass index (BMI) under 35 - the marker at which people are considered seriously overweight by the NHS - should have their waist measured.
There should also be respect for individual privacy such as at a regular weigh-ins.
According to Nice, dealing with the long-term consequences of obesity costs the NHS an estimated £5.1 billion every year, "placing a huge strain on the health service".
Professor Mike Kelly, director of the centre for public health at Nice, said: "Being overweight or obese can have serious consequences for an individual's health, not only physically with increased risk of high blood pressure and type 2 diabetes, but it can also affect their mental health as a result of stigma and bullying or discrimination.
"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 new draft guidance focuses on the provision of effective lifestyle weight management services and makes a number of recommendations to ensure that the providers of programmes whether from the private, public, or voluntary sector follow good, evidence-based practice.
"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."