In the light of a Food Commission report showing that a large pot of KFC coleslaw contains 22.4g of fat - more than its fillet burger (15.6g) or large fries (19.4g) - it is perhaps reasonable to wonder that if a mix of shredded cabbage, carrot and mayonnaise isn't a healthy option, what on earth is?

"No one is expecting a burger and chips to be super-healthy," says Anna Glayzer from the Food Commission. "However, I think a lot of people would be surprised to find out just how unhealthy some fast-food options are."

A survey of leading nutrition and obesity experts bears this out, with none of the 66 specialists capable of telling from a menu description which item was the least healthy option.

Confusion often stems from nutritional truth running contrary to accepted food wisdom. After all, surely vegetarian options are healthier? Not if you choose the Subway Veggie Patty Sub, which has more calories than either the steak and cheese sub, or the turkey, ham, bacon and cheese sub. Salads healthier than burgers? Not if you pick the McDonald's crispy chicken and bacon salad, which has 15g of fat per portion, almost twice as much fat as a simple hamburger (8g). It's not just restaurants that turn choosing food into a health minefield: a healthy-sounding cereal such as Jordans Organic Granola contains 15g of fat per 100g and Which? found that Asda's Good for You Beef Lasagna was as high in saturated fat as its standard lasagne.

But at least with supermarket food fat content is usually on the packet. Until the Food Commission achieves its ambition of nutritional information at point of sale, health-conscious fast-food fans will have to follow the advice of Dr Nick Riviera from The Simpsons: "If you're not sure about something, just rub it against a piece of paper. If the paper turns clear, it's your window to weight gain."