Health groups are urging food companies to disclose added sugars on product labels, saying this will lead to more accurate health star ratings and win back consumer trust.

Researchers at the George Institute for Global Health analysed more than 34,000 products and found 70 per cent contained added sugars, which they say are simply "empty calories" contributing to Australia's obesity epidemic.

They calculated two health star ratings – one using total sugars (as is current practice) and one using added sugars.

"We know there are problems, anomalies with the ratings system," said co-author Professor Bruce Neal. "But by using added sugars, we found higher ratings were given to good foods and lower ratings to unhealthy foods."