A big fat 'marketing scam' ?

The Heart Foundation tick can be given to products containing high levels of sugar or salt. Photo / Herald on Sunday.

Shoppers who plump for low-fat food and drink choices are being warned they're victims of a "marketing scam".

A Herald on Sunday survey of everyday products advertised as low-fat or fat-free revealed some were almost one-third sugar.

Eta Lite & Free mayonnaise is promoted as 98 per cent fat-free and carries the Heart Foundation tick - despite containing 6 grams of sugar a serving, about the same as a Toffee Pop.

Kellogg's Crispix breakfast cereal is labelled 99 per cent fat-free but is 32 per cent sugar. That's almost 10 grams in every serving, as much as in a 100ml glass of Coke.

AUT University professor of nutrition Elaine Rush said such products could contain a high level of salt as well as sugar

She said low-fat branding was a "marketing scam" that led consumers to focus on what wasn't in their food, rather than what was.

And she urged shoppers to check the level of saturated fat rather than total fat content.

"Don't worry so much about the other fats, because you want to have that flavour come through, and you've got to have a certain amount of fat in your diet."

The Heart Foundation's Dave Monro said the Eta mayonnaise was likely to have earned the tick for being lower in saturated fat and salt than comparable products.

He agreed shoppers should check the full list of ingredients rather than the fat content alone.

"It makes it really difficult if you just look at one ingredient like that, because you can leave out important things like the sodium level."

Some breakfast cereals that were low in sugar and fat could have "as much salt as a bag of chips", he said.

Nutrition Foundation chief executive Sue Pollard said fat-free labelling was "tricky" for consumers, and serving size was the key.

"If you're eating more of a low-fat food, you may end up eating the same amount of energy."

Pollard said detailed labelling - such as average daily intake tables - could be helpful but may be too much for some shoppers to take in.

"In the end, people still buy based on taste and price," she said.

Shoppers said they tried to be cautious of fat-free claims.

"Buying 'lite' doesn't really mean buying 'lite'," said Bridgitte Lister, 32.

"People think it's low fat but it can be high in sugar."

Student Katie Brown said she sometimes checked the total kilojoules, "but other than that I just buy what I like," she said.

"If it's fat-free it should really be low in sugar, but it isn't always."

Monro said manufacturers had to decide whether it was appropriate for products, like sugary lollies, to carry fat-free claims.