University study points to high fat, sugar, sodium and calorie levels and obesity risk.
Some of New Zealand's favourite burger-chips-and-drink combos are fuelling our overfed nation up with more than 40 per cent of the energy recommended for an average adult for a whole day.
Based on the World Health Organisation's suggestion that maximum sugar intakes could usefully be halved, the combos were found to pack a sugar hit of 94 to 185 per cent of recommended daily sugar consumption.
Based on these findings, Dr Helen Eyles and her University of Auckland colleagues who conducted the research concluded in the New Zealand Medical Journal that "there is plenty of room for improvement in the nutrient composition of fast-food items in NZ".
They did an online survey of 104 adults in January to identify the most-loved fast foods at KFC, McDonald's, Pizza Hut and Burger King. They analysed the composition of the 14 most popular menu items.
For a typical woman, the four Burger King combos that made the favourites list carried between 35 and 54 per cent of the recommended daily intake of energy and 137 to 185 per cent of the recommended daily limit for sugar.
The McDonald's favourites would give her 31 to 41 per cent of her recommended daily energy.
The WHO says New Zealand experienced the fourth-greatest growth in fast-food purchasing among 25 high-income nations from 1999 to 2008. All 25 also increased their weight for height - and NZ was well in front with an increase of more than one point on the body mass (BMI) scale on which a score of 25-29.9 is overweight and 30-plus is obese.
In New Zealand, 31 per cent of adults are obese and 34 per cent are overweight. Our spending on takeaways rose by a quarter in four years, to $1.5 billion in 2012, according to industry data.
Dr Eyles and her colleagues said: "The rise in fast-food availability and consumption is concerning because this food is generally high in fat, sugar, sodium [part of salt] and energy, and high intakes are associated with increased body mass index ... and obesity risk.
"As such, there have been calls for guidelines around the nutrient composition of fast food and availability of healthier options."
The researchers found salads were offered at Burger King, McDonald's and KFC and on most nutritional measures had the healthiest profiles of main menu items. But salads were not popular in their survey.
"... no one indicated they had consumed a salad from one of the four fast-food chains in the past month."
A McDonald's spokeswoman said the chain supported a multi-sector approach to obesity, which was a complex issue. She criticised the study's design, which was "focused on one purchase, and provided no context of the person's overall diet".
"On average New Zealanders eat at McDonald's once a month. For over 10 years, McDonald's has reformulated its menu to reduce sugar, sodium and saturated fat, without impacting taste and quality ... We have added new menu items to provide choice ... [such as] a popular new range of salads and wraps ..."
A Burger King spokeswoman, Rachel Morriss-Jarvis, said energy labels had been introduced on menu boards last year to help customers make informed choices. There had also been significant improvements to the range available, including salads, wraps and low-fat options.
"As the WHO guidelines have just been released, we will review in line with our ongoing menu improvement processes which aim to reduce salt, sugar and energy from our menu," she said.
No one at Restaurant Brands, which operates Pizza Hut and KFC, could be reached for comment.