Dr Muffazal Lakdawala of Saifee Hospital and his team performed the surgery on Daulatram Jogawat, who weighs around 180 kg.
Ms De had tweeted a picture of an overweight Mr Jogawat in uniform, mocking the Mumbai Police for "heavy bandobast" on a polling day.
Mumbai Police promptly pointed out that he was an inspector with the Madhya Pradesh Police. The storm on Twitter over this prompted Dr Lakdawala to offer help to Mr Jogawat.
"His condition will be reviewed by Dr Lakdawala tomorrow and he may be discharged in the next couple of days," said Zoya Suterwala of Saifi Hospital.
Mr Jogawat will have to be on a liquid diet for the next 15 days, Ms Suterwala added. Gastric bypass surgery is aimed at reducing the volume of the stomach to curb the food intake.
Before the surgery, Mr Jogawat admitted that one wrong tweet had changed his life. "I am thankful to my senior officers and the media for this. A wrong tweet has changed my life," he said.
"I was hurt by the tweet poking fun at me. I put on weight due to a hormonal disorder following a gall bladder operation in 1993," he said.
Shobha De, who faced some heat on social media for fat-shaming a person, later tried to make amends. "No offence intended. MP Police, Consult a dietician, if it's an asli, undoctored image doing the round," she said.