Auckland nutritionist Lynda Smith said Burger King's move was positive because a lot of people were unaware of how much energy was in their food.
"It could influence what they buy - they might perhaps buy a smaller serve of fries or perhaps another type of burger, not such a high-energy burger."
Nutrition Foundation dietitian Sarah Hanrahan said displaying the energy in kilojoules was a "great place to start".
"It's a good first step, but you could go further. You do need context around it."
She urged fast food restaurants to adopt the healthy star rating system - an interpretive system endorsed by the Government which will be adopted voluntarily.
"That would give people further information. It would help them make perhaps some better choices."
Mr Hunter said Burger King had been providing nutritional information on its website and in-store for years.
"Our customers told us that they wanted more information, so we looked at ways we could improve our service. The result was a nationwide initiative to include energy labelling on all our menu boards."
A McDonald's spokeswoman said the chain had no plans to do the same, but it was focused on giving customers meaningful nutritional information they could understand.
It already provided detailed information on tray mats, select packaging and its website. McDonald's was also looking closely at the new health star rating system.
A Subway spokesman said its stores would not follow suit. The company supported a consistent national approach to labelling at all fast food outlets, so customers could make an informed choice across the board.
It had long supported providing nutritional information to customers, with information available on its website, napkins, counter displays and in brochures.
A spokeswoman for Restaurant Brands, which operates Carl's Jr and KFC in New Zealand, said nutritional information was available on their websites. KFC also had nutritional brochures available in store.
Pita Pit said it did not have any immediate plans to display nutritional information on menu boards but was looking at ways to give information. McDonald's and Burger King both said they had worked to improve the nutrition of their products and introduced healthier options. Subway and Pita Pit said they provided healthy options.
