Dolmio pasta sauce.
Reduced: Dolmio pasta sauce has downsized by 75ml. Photo: Ken James

Pasta sauce jars are getting lighter, man-size tissues have shrunk and chocolate bars have lost weight.

Food and product manufacturers are reducing the size of their food portions and products but still charging customers the same prices, in what consumer groups say is a bid to expand their profits.

Kleenex man-size tissues were awarded a Shonky award last week by consumer group Choice for shrinking their tissues by 14 per cent, despite charging the same amount, about $4.

Cadbury Dairy Milk.
All over the place: The size of a standard Cadbury Dairy Milk block has changed several times in recent years. Photo: Supplied

''They had a well-established brand around man-size and it meant a certain size tissue, and then without telling consumers they have shrunk the tissues,'' Choice spokesman Tom Godfrey said. ''A small reduction in the size of a popular product can result in big savings.''

In June, Dolmio began to reduce its pasta sauce jar size by 75 millilitres, with parent company Mars justifying the change as a healthier option.

"The transition to a 500-gram jar is part of our investment in providing healthier products across all our categories,'' a Mars spokeswoman said.

Cadbury said it recently increased the size of its chocolate blocks from 200 grams to 220 grams, while keeping the same price, but only after it decreased the size from 250 grams in 2009.

In September, Fairfax Media revealed takeaway coffee cup sizes had also begun shrinking, with no change in price. Coffee shops offered their regular coffee with 60 millilitres less milk, saying they were giving a premium-tasting coffee.

Five years ago Cherry Ripe chocolate bars were reduced from 55 grams to 52 grams, a Cadbury spokeswoman confirmed.

Tim Tam packs now come in three sizes: 11, nine and five biscuits. The five-biscuit pack has been designed for ''snackers'', an Arnott's spokeswoman said.

For years Tim Tam eaters thought they were being ripped off on the assumption the 11-biscuit packet had been reduced from an even dozen.

Mr Godfrey said food manufacturers sometimes shrank the portion size of a product to maintain profits ''without appearing to raise prices''.

According to the Obesity Policy Coalition, a quarter of Australian children and 62 per cent of adults are overweight or obese.

Executive manager Jane Martin said she would rather see a health labelling system than a reduction in size to combat obesity.