Move over butter coffee, get out of the way green smoothie. Fat-infused water is the new health drink in town.

Know simply as FATWater, the 84 kilojoule concoction is the latest invention from Silicon Valley-based "bio-hacker" David Aspey, creator of the Bulletproof Coffee craze which saw people across the globe adding butter to to coffee in an effort to improve their health and boost their brain power.

A standard 473 mL bottle of the FATWater (marketed as "paleo" and gluten-free and priced at around $5) is little more than standard water mixed with two grams of saturated fat-rich coconut oil.

Asprey claims FATWater rehydrates the body quicker because cells are more receptive to water containing a tiny bit of fat.

"The oils enhance thermogenesis, which is a fancy word for 'fat burning,' " said Asprey speaking to the New York Daily News. "They get burned as energy and have an appetite-suppression effect. It's not like we put in sunflower oil or canola."

But dietitian Susie Burrell said the concept of drinking water mixed with saturated fat for health reasons was "ridiculous".

"There is no health benefit associated with eating fat in isolation, let alone saturated fat," she says "With 70 per cent of Australians chronically dehydrated, we are best just to concentrate on plain old water - its free, cheap and will make us feel 100 per cent better just by drinking more of it on a daily basis."

Unlike Bulletproof Coffee, FATWater is not yet available in Australia, although it can be purchased in concentrated form from the Bulletproof website.