Parmalat, the food giant behind Vaalia and Ski yoghurts, has ranked last in a study that examined the obesity prevention efforts of Australia's biggest food and beverage manufacturers, scoring a derisory three out of 100.

With an alarming two-thirds of adults overweight or obese, Deakin University researchers ranked Australia's top 19 food and drink companies based on health-related policies in areas such as product formulation, nutrition labelling and advertising to children.

Scores ranged from three to 71 out of 100, with four companies - Parmalat, Goodman Fielder (owner of Helga's bread), Schweppes (Spring Valley juice) and Tru Blu (LA Ice cola) - scoring below 10.

Parmalat, the maker of Vaalia yoghurt, ranked last in the Deakin University report.

"For sure, we're all responsible for what we buy and eat, but we also know that our environment, which is dominated by heavily promoted, cheap and unhealthy foods, influences our choices," lead author Associate Professor Gary Sacks from Deakin’s Global Obesity Centre said.