An Egyptian who is believed to be the world's heaviest woman is to fly to India for weight reduction surgery after the country's foreign minister personally intervened to secure her a visa.

Indian surgeon Muffazal Lakdawala had offered to carry out the procedure free of charge after hearing about Eman Ahmed Abd El Aty, who weighs around 500 kilogrammes (1,100 pounds).

But her request for a visa was initially rejected, prompting Lakdawala to tweet a request for help to India's foreign minister Sushma Swaraj.

"She is a bundle of diseases. She needs surgery urgently," the surgeon said of Abd El Aty, 36, who is expected to fly to the western city of Mumbai next week for the procedure.

"Her sister said she hasn't left her room in 25 years. I just thought 'Oh my god, I have to help. I'll do it pro bono, no problem'."

Lakdawala said he was astonished when Swaraj, who is herself ill in hospital awaiting a liver transplant, replied to his plea within hours.

Abd El Aty's sister had approached him about two months ago, saying her sister needed urgent medical attention.

Her family told the doctor that as a child she was diagnosed with elephantiasis, a condition that causes the limbs and other body parts to swell, leaving her almost immobile.

Later she suffered a stroke and was rendered bedridden, triggering a series of ailments including diabetes, high blood pressure, hypertension and sleep apnoea.

Lakdawala, who has operated on government ministers in the past, said he was nervous but would do all he could to make Abd El Aty comfortable.

"I would be lying if I said I was 100 percent confident. There are many challenges, but I will try my level best to help her," he told AFP by phone.

Abd El Aty would need a couple of months in post-surgery care in India before heading back home in Egypt, he said.

Bariatric surgery is essentially a stomach-shrinking bypass procedure carried out on those wanting to lose excessive weight.

It is increasingly common in India, which has a growing problem with obesity, particularly in urban areas.

India is a key destination for medical tourists because it offers quality services at a fraction of the cost of western countries and no waiting lists.