A Mediterranean diet may be a better way of tackling obesity than calorie counting, leading doctors have said.
Writing in the Postgraduate Medical Journal (PMJ), the doctors said a Mediterranean diet quickly reduced the risk of heart attacks and strokes.
And they said it may be better than low-fat diets for sustained weight loss.
Official NHS advice is to monitor calorie intake to maintain a healthy weight.
Last month NHS leaders stressed the need for urgent action to tackle obesity and the health problems that often go with it.
The PMJ editorial argues a focus on food intake is the best approach, but it warns crash dieting is harmful.
Signatories of the piece included the chair of the Academy of Medical Royal Colleges, Prof Terence Stephenson, and Dr Mahiben Maruthappu, who has a senior role at NHS England.
They criticise the weight-loss industry for focusing on calorie restriction rather than "good nutrition".
Better than statins
And they make the case for a Mediterranean diet, including fruit and vegetables, nuts and olive oil, citing research suggesting it quickly reduces the risk of heart attacks and strokes, and may be better than low-fat diets for sustained weight loss.
The lead author, cardiologist Dr Aseem Malhotra, says the scientific evidence is overwhelming.
"What's more responsible is that we tell people to concentrate on eating nutritious foods.
Inspired by traditional cuisine of countries such as Greece, Spain and Italy, the Mediterranean diet has long been associated with good health and fit hearts.
Typically, it consists of an abundance of vegetables, fresh fruit, wholegrain cereals, olive oil and nuts, as well as poultry and fish, rather than lots of red meat and butter or animal fats.
"It's going to have an impact on their health very quickly. We know the traditional Mediterranean diet, which is higher in fat, proven from randomised controlled trials, reduces the risk of heart attack and stroke even within months of implementation."
The article also says adopting a Mediterranean diet after a heart attack is almost three times as effective at reducing deaths as taking cholesterol-lowering statin medication.
The authors argue the NHS is in a "key position" to set a national example by providing healthy food in hospitals and by ensuring doctors and nurses understand the evidence.
Prof Stephenson says the service can exert a powerful influence, for good or ill.
"Our hospitals and surgeries are the frontline for delivering health, it's nothing more than common sense then that we should be leading by example.
"We wouldn't dream of letting people drink alcohol or smoke in any healthcare environment, so I find it incomprehensible that we facilitate and sometimes actively promote food and drink that in some ways cause as many problems. And although some positive steps have been taken on the food given to patients in hospital, their visitors and staff also deserve better."
Public Health England is reviewing the dietary advice conveyed in the "eatwell plate" - which is used across the UK for guidance on what food to eat. Its recommendations include calorie-counted recipes to help achieve a healthy weight.
Dr Alison Tedstone, the chief nutritionist at Public Health England, said there was no single silver-bullet solution.
"Government advice is to eat plenty of bread, rice, potatoes, pasta and other starchy foods, plenty of fruit and vegetables; and some milk and dairy products, meat, fish, eggs, beans and other sources of non-dairy protein.
"Foods high in salt, fat and sugar should be eaten less often and in small amounts. If you are currently overweight you will need to eat less to achieve a healthy weight and be active as part of a healthy lifestyle."
The chairman of the National Obesity Forum, professor David Haslam, welcomed the article.
"A calorie is not just a calorie and it is naive for anyone to think the complex hormonal and neurological appetite systems of the body respond to different substances in the diet in identical fashion."
He said banning fast food outlets in hospitals would be a "legal minefield" given the extended contracts in existence. But he said healthy nutrition programmes could be put in place - as has happened in other big organisations - to counter what he called their "sinister effect".