Weight-loss drugs containing a toxic chemical known as 'shredders' have been linked to numerous deaths in Australia and overseas, health authorities have warned.

NSW and ACT Health have warned people to avoid weight-loss products which contain the chemical, 2,4-dinitrophenol, or DNP.

Several deaths from taking DNP have been reported overseas and more recently in Australia, NSW Health said, but no further information has been released.

The chemical, which can make people sick within hours, prevents energy from being stored as fat, instead releasing it as heat and increasing body temperature which can damage organs such as muscle, kidney and brain.

Clinical Toxicologist and Intensive Care Physician at the NSW Poisons Information Centre, Dr Kylie McArdle, said DNP was an extremely toxic substance.

"There's a myth that if used in small amounts, users will be safe," she said.

"There is no antidote and even with our best medical care, people can and have died using products containing the chemical."