Fast food sold in Australia is just as unhealthy despite the introduction of mandatory menu labelling, according to new analysis.
A study by Cancer Council NSW and The George Institute for Global Health found the kilojoule content of foods sold at the top five food chains - Hungry Jacks's, KFC, McDonalds, Oporto and Red Rooster - has not changed since 2009.
Researchers tracked the kilojoule content per serving and per 100 grams of fast food menu items sold at the major chains in March and April every year for seven years from 2009 to 2015.
"We found that overall, there was no significant or systematic reduction in kilojoule content since the introduction of menu labelling in NSW," Clare Hughes, Nutrition Program Manager at Cancer Council NSW, told AAP.
"There were some fluctuations in kilojoule content of individual items but when we assessed product categories, when we assessed particular chains it was really clear that there was no systematic change."
Menu labelling was introduced in NSW in 2012 and since adopted in four other states and territories in response to rising obesity rates.
This means that any fast food restaurant with 20 or more stores across the state or 50 or more nationally has to show kilojoule information on menus and displays in their restaurants.
The evidence shows labelling works to help customers make healthier choices. A recently published Cochrane Library review of menu labelling in restaurants and coffee shops found the obesity intervention reduced calorie consumption by around eight to 12 per cent per meal, which equates to nearly 50 kcal.
Despite this and in light of the new Cancer Council research, public health experts want the government to work with the fast food industry to reformulate the food they produce which is commonly high in sugar and fat.
Ms Hughes says reformulation has the potential to significantly improve fast food consumers' energy intake and "it's now time" for the industry, with pressure from governments, to make some meaningful changes to the food sold in fast food outlets.
"The foods that we eat away from home at some of these outlets can make a significant impact on a person's nutrition intake across the week, across the month and across the year which really has an impact on our health," she said.