Brexit is an opportunity to make traffic light labelling on food and drink packaging mandatory to help consumers make informed choices, councils have said.
EU legislation currently regulates food and drink labelling, and in 2013 the Department of Health introduced the voluntary traffic light scheme that allows consumers to see at a glance how much fat, saturates, sugar and salt a product contains.
However the Local Government Association (LGA), whose councils have responsibility for public health, said the labels are only carried on two thirds of products sold in the UK.
It said the traffic light system should become a legal requirement for all products once EU laws are transferred into British law after Brexit to allow consumers to make healthy food choices.
Izzi Seccombe, chairwoman of the LGA's community wellbeing board, said: "The traffic light food labelling system is clear, effective and popular with shoppers.
"While many retailers and manufacturers have different methods of displaying nutritional content, this can be confusing. As a result, shoppers are unwittingly buying products which are laden with fat, salt and sugar, which is fuelling the obesity crisis.
"Any post-Brexit review of EU food laws gives the Government the opportunity to introduce legislation to standardise food labelling.
"At a time when two thirds of adults and more than a fifth of four and five year olds are obese or overweight, helping people make more informed choices about what they eat will clearly also help tackle the obesity crisis we face as a nation."