Aggrieved patients and healthcare professionals have complained about Dr Thomas Goyer and the institute with the Medical Council of NSW, the ACCC, Fair Trading NSW and the Health Care Complaints Commission.

Former patients claim they paid up to $3500 but failed to lose more than a couple of kilos despite sticking to the institute's drug regime and low-carb diet. They say they were prescribed drugs and vitamins without ever meeting a doctor or having their medical history taken, and were promised extreme weight loss on the program.

While he is being investigated by health authorities, Dr Goyer has been banned from prescribing the peptide human chorionic gonadotropin, which studies dating back to the 1970s have found was no more effective for weight loss than a placebo.

Obesity expert Professor John Dixon, from Baker IDI, said there was nothing in the drug regime prescribed to Ms Crosby that was new or proven to aid in weight loss.

"HCG is a pregnancy hormone, the spruikers of HCG have been around for decades," he said. "There have been HCG trials and they didn't work."

Despite the lack of evidence, Fairfax Media has seen client emails in which a MWI program manager claims the HCG drops were a weight loss tool that "works by suppressing the appetite and increasing your metabolism".

Other medications prescribed by the institute include a compound of caffeine, low doses of diabetes drug Metformin and the plant extract garcinia cambogia.

Professor Dixon said the Metformin may lead to a loss of up to 1kg in some people and that unproven appetite suppressant properties could be present in the garcinia cambogia. "But it is clear it does not assist weight loss," he said.

South Australian pensioner Christina Crosby paid $2500 after a loss of 15 kilos in 10 weeks "was guaranteed", she said.

Ms Crosby said the medications were sent to her before the institute would have received the results of a blood test that clients were told determined their personalised "meds".

"I should have spoken to my doctor but at the time I felt like a blimp, I was desperate and the person on the phone promised me all sorts of things, that I had nothing to lose, I wanted it to work," she says.

The company behind MWI is GTC Medical, which is owned by its three directors: a nurse, Dr Goyer and a man listed on the clinic's website as the CEO and head of psychology: Chibuzo Okereke.

Two out of three directors have been linked to failed erectile dysfunction clinics.

Mr Okereke previously part-owned the sex drug spruiker Supplemax Pty Ltd, which collapsed under the weight of more than 200 misleading and deceptive conduct complaints in 2011.

Before turning to weight loss, Dr Goyer worked for the Advanced Medical Institute, which the Federal Court last year found had engaged in unconscionable conduct by selling questionable premature ejaculation and impotence drugs to vulnerable men.

The public face of  the Medical Weightloss Institute, sports scientist Geoff Jowett, was last year declared bankrupt.

In a video since removed from the internet, Mr Jowett had warned potential clients their GP may not understand MWI's program because "they don't know what we know".

Dr Goyer resigned as the clinic's medical director on July 14 and as a director of GTC on July 22.

Attempts to contact him through his Sydney clinic were unsuccessful.

Mr Obereke could also not respond to questions because he was overseas, the MWI spokeswoman said.

A spokesperson for the NSW Healthcare Complaints Commission said it was investigating a complaint about Dr Goyer.