If the sudden death of cricketer Shane Warne sent shockwaves around the globe, the subsequent revelation that the spin bowler was on a "fluid-only" diet for two weeks prior has sounded the alarm on the dangers of extreme dieting for heart health.

After Warne's death from a suspected heart attack in Thailand, his manager James Erskine said the cricket legend had recently finished a "ridiculous diet" where he consumed only "black and green juices" for two weeks.

Nicole Bando, an accredited dietitian based in Melbourne, said so-called "detox" or "juice" diets were potentially dangerous because they involve the removal of whole food groups, including important nutrients, from a person's diet.

"If you do [a juice diet], it can actually lead to a dilution in electrolytes — which are the salts in our blood," she said.

"These include potassium which is involved in conducting electricity, and therefore the function of the heart."

Professor Garry Jennings, chief health advisor at the Heart Foundation of Australia, said such diets introduced the possibility of heart complications.

People with other underlying conditions — such as diabetes, kidney and liver problems — are also at risk of "severe consequences", Professor Jennings added.

"What can happen [with extreme dieting] is that if the heart is not bathed in the right mixture of electrolytes and nutritional chemicals, then your heart gets more irritable.

"So if you were to have a heart attack, it's much more likely to lead to something more serious, such as cardiac arrest."

Another issue with extreme diets, Ms Bando said, is what happens when they "end".

"When you reintroduce normal foods you can actually cause a further imbalance of electrolytes," she said, referring to a phenomenon known as "re-feeding syndrome".

"When normal eating is resumed, it can cause the levels of these salts to drop because they're being used in the metabolism of the food."

On the extreme end, she said, this can lead to heart arrhythmia (irregular heartbeat) as well as seizure, coma and death. Less severe symptoms include headaches, fatigue and nausea.

One of Warne's friends yesterday revealed the cricket legend had eaten Vegemite on toast just hours before his death.

Another problem with extreme diets, Ms Bando said, was the myth that they "detoxify" the body — a process our bodies naturally undertake anyway.

"Our body's incredibly evolved. From the skin to the gastrointestinal system, to our kidneys, lungs and liver, they all remove various toxins from our diet, whether that comes from food, or internal toxins that are by-products of metabolism."

Those drawn to fad dieting because of the promise of weight loss, Ms Bando said, would be better off focusing on a "balanced" approach to nutrition.

"The weight loss that occurs is usually short-lasting. And then when people revert to their usual diets, they tend to regain the weight."

Professor Jennings agrees.

"If you look at any recommendation from any authority around the world, it's about a balanced diet with all the main food groups," he said.

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