LONDON - Healthy options offered by leading burger and pizza chains in Britain are still stuffed with salt and fat, despite attempts to makeover the menus.
Companies like McDonald's have made great play of introducing healthier options such as salads, amid mounting concern over levels of obesity.
However, an investigation into the food sold by the "Big Four" - MacDonald's, Burger King, KFC and Pizza Hut - found that 17 out of 20 products were high in salt or saturated fat or both.
Of those, five out of eight of the salads paraded by the companies as evidence of their embrace of healthy eating had "high" salt or fat content.
On average the fast food meals sampled by Which? had 274 calories per 100g of food - more than double the amount in a home-cooked roast dinner.
The research found inaccuracies in the nutritional information provided by three of the companies. McDonald's website claimed that a Big Mac and medium fries had 786 calories, but analysis showed that it had 900.
Burger King's Whopper and regular fries had 19g saturated fat, rather than the 13g claimed by the American giant. Levels of saturated fat in KFC's Zinger crunchy salad were almost treble the company's estimate.
"Don't assume that a salad is always a healthy option - you could be getting a large helping of fat and salt on the side," warned Malcolm Coles, editor of Which? magazine.
Which? said that although fast food was not solely to blame for obesity, the expansion of waistlines had been accompanied by the rise in fast food.
In a survey of school children, the consumer organisation found that the popularity of fast food joints was related to the size of their advertising budgets.
Which?, formerly the Consumers' Association, analysed the nutritional content of the Big Four's products. It found that Burger King fries were only 86 per cent potato - the 11 other ingredients included partially-hydrogenated vegetable oil, rice flour, dextrose, corn syrup solids and salt.
Although McDonald's chicken grills "looked like pieces of simple grilled chicken breast", they contained 19 other ingredients. McDonald's and Burger King's cheddar cheese slices included "cheese flavouring", trisodium citrate, diphosphates, polyphosphates and sorbic acid.
Some of the fast food meals were extremely calorific. A McDonald's Big Mac, medium fries and small vanilla milkshake contained 1169 calories.
Which? said: "Nearly all the fast food we tested contained a lot of salt per portion. And salt can lurk where you least expect it. The KFC original chicken salad contains more salt than the KFC chicken fillet burger."
A Pizza Hut margherita pan pizza and garlic bread had 5.4g of salt - almost the entire recommended daily allowance of 6g.
In response, the companies said that their menus had more variety than in the past. Pizza Hut said that its menu gave customers "the choice of healthy or more indulgent food".
Tim Lang, Professor of Food Policy at City University, said: "The food industry knows there is evidence of a health problem which it is part of, but it likes to claim it has nothing to do with it."