The sister of Eman Abd El Aty, an Egyptian woman thought to have been the world's heaviest, has accused doctors of lying about her weight loss after surgery in India.
She underwent surgery in Mumbai's Saifee hospital, and last week doctors said she had lost 250kg (550lbs).
But her sister said this was untrue, adding that her sister was in delicate health as she may have had a stroke.
The hospital has angrily rejected the allegations.
The row began on Monday when Ms Abd El Aty's sister, Shaimaa Selim, released a short video on social media, alleging that her sister was still unable to speak or move, and had not lost as much weight as the hospital was claiming.
On Tuesday, she told the BBC that the hospital was lying about her weight loss.
"He [Dr Muffazal Lakdawala, who led the operation] didn't weigh her before and after. If he has any proof of her weight loss, show us the video of her weight before and after."
Describing her sister's health as delicate, she said: "Oxygen is not normal in her body. She has to wear an oxygen mask almost all the time. There is a tube from her nose to her stomach because she can't eat or drink well from her mouth.
But a spokeswoman for the hospital told the BBC that Ms Abd El Aty was weighed again on Monday and she now weighed 172kg.
Dr Lakdawala also strongly denied the allegations in a tweet.
Eman Abd El Aty suffered a stroke at the age of 11 and her weight meant she was unable to leave her home for 25 years.
She was flown in a special aircraft in January to Mumbai's Saifee hospital where she underwent bariatric surgery in March by a team of doctors, led by Dr Lakdawala.
The hospital says she can now fit into a wheelchair and sit up for longer periods of time. It released new pictures of Ms Abd El Aty following weight reduction surgery.
Reports say Ms Selim is unhappy because the hospital authorities believe that Ms Abd El Aty's treatment is almost over and that she can be sent home to Alexandria soon.
"There are cases like this in other parts of the world. In America and in other countries, there are heavyweight people. They have been in the hospital for one or two years to lose weight and become normal.
"But just after a month or two here, the doctors say that I can take my sister back. I asked them how, as she is still very big and if anything happens to her in Egypt, how can I go to a hospital there?
"It would be impossible and nobody would help me in Egypt. I said, 'Please please keep her for a long time to help her lose weight'," her sister said.
Bariatric surgery, also known as weight loss surgery, is used as a last resort to treat people who are dangerously obese (having a body mass index of 40 or above, or 35 with other obesity-related health conditions).