Westpac said some people were persuaded to hand over money but ended up with a fake product, or nothing at all.
The bank urged people to be wary of weight loss or health claims that seemed too good to be true.
It also advised people to carefully read all terms and conditions before signing up to any subscription for a diet or supplement product.
“Make sure you understand the cancellation policy, fees and dispute resolution process,” Westpac added.
The bank urged people to check online reviews of businesses and products, and if keen to lose weight, seek health advice from a trusted healthcare professional.
Westpac earlier this summer warned customers about Christmas scammers.
“They may ask you to pay for online goods that are never delivered. Sellers can also be duped with payments that never arrive.”
People were urged to be wary of odd payment methods on online marketplaces, and be wary of trading if a seller had a fairly new profile, bad feedback or limited friends.
“Be wary if you’re asked to complete a trade off-platform.”
Catfishing is another popular holiday season scam.
The romance scam involves people impersonating a handsome or beautiful suitor, and using charm and deception to get money out of a target.
A reformed catfish scammer last month told the Herald he tricked a woman out of tens of thousands of dollars.
He advised people not to look for love online, but if they insisted, to always request videocalls to verify the identity of their online contacts.
