Weight is lost rapidly through ketosis, a state where the body burns fat instead of sugar, he says. All patients are monitored over the 10-day period, during which they often experience side effects like dizziness, bad breath and constipation.
Auckland-based dietitian Mary Rose Spence says although the trend has not yet reached New Zealand, the diet should be ticked up as another fad.
"These people are not going to have long-term success. There is absolutely no doubt, 100 per cent of these women will put the weight back on which will be a disappointment for them."
Spence says a lot of women come to see her before their weddings, wanting to lose weight before the big day.
"The first thing I say is that there is a bigger issue," she says.
"It's important to encourage good patterns that will keep the weight off for the rest of their lives, and to pass these on to other family members."
She also expressed concerns about the protocol around nasogastric feeding and hygienic issues as the procedure, when it is used in hospitals, has to be closely monitored and can be dangerous.
Despite the risks, the diet is gaining popularity in the US. With a price tag of US$1500 (NZ$1825) it's not cheap either - but women are willing to pay for it.
Jessica Schnaider told ABC News why she chose the K-E diet.
"I don't have all of the time on the planet just to focus an hour and a half a day to exercise so I came to the doctor, I saw the diet and I said. 'You know what? Why not? Let me try it."
Schnaider lost about 5kg after only eight days on the regime.
The controversial diet has copped criticism from health professionals.
"Any extreme low-calorie diet is associated with side effects, kidney stones, dehydration, headaches," said Dr Louis Aronne, director of the Comprehensive Weight Control Program at NewYork-Presbyterian medical centre.
"And if you lose muscle mass and water, what's the point of that?"
Dr De Pietro has defended his work to critics.
"It's a hunger-free, effective way of dieting," he told ABC news.
"Within a few hours your hunger and appetite go away completely, so patients are actually not hungry for the whole 10 days. That's what is so amazing about this diet.
"At first I decided not to do it for people who just want to lose a few pounds. But then I thought, why should I say five or ten pounds are not enough? People want to be perfect," he told the New York Times.
Pre-wedding drastic dieting is nothing new. Fads of the past have included the Atkins diet, "cleaning" detoxes of water and maple syrup and even injections of human chorionic gonadotropin.
