Diet replacement programmes made up of low-calorie soups, shakes and regular counselling should be a recommended NHS treatment for obesity, a BMJ study says.
People on the diets lost three times more weight than those devoted standard dietary advice by their GP, University of Oxford researchers found.
And their risk of developing heart disease and type-2 diabetes reduced.
But experts said it would work only if eating habits were changed for good.
Prof Paul Aveyard, analyse writer, GP and professor of behavioural medicine at the University of Oxford, said losing weight and maintaining it off was hard.
“It’s bearing being on a normal diet and people struggle to stick to it for a year, ” he said.
“But these programmes get you when your mental strength is at its highest.
“You have to concentrate effort into 12 weeks and because they feed so little, they lose a lot of weight quickly.”
Total diet replacing programmes are designed for people who are obese or seriously obese, with a body mass indicator( BMI) of more than 30, who have been unable to lose weight despite changes to diet and lifestyle.
They are currently only available privately – although NHS England has said it is considering the diets as part of a long-term plan for the NHS.
BMI and obesity: Where are you on the UK fat scale ?~ ATAGEND a chocolate-flavour skimmed milk and soya protein shake mixture( 145 kcal) chicken-and-mushroom-flavour skimmed milk and soya protein soup mix( 138 kcal) skimmed milk and multi-wholegrain porridge mix( 149 kcal) lemon-flavour soya and milk protein bar covered in yoghurt-flavour coating( 150 kcal) Image caption