ZAPOPAN, Mexico (AFP) - A Mexican man believed to be the world's most obese plans to undergo gastric bypass in the new year and reduce his weight - 590 kg - by half, his doctor said.

The man known as Juan Pedro has diabetes, high blood pressure and chronic lung obstruction, and needs to reduce his weight dramatically to reduce his health risks, Dr Jose Castaneda Cruz said on Wednesday (Dec 21).

He said the man, who does not give his family names to media, would actually undergo a couple of procedures along the way.

"It's a surgery that is going to be done in two parts. That is because of the high risk of complications he faces. So it's going to be done in two parts, six months apart," Dr Castaneda told reporters.

In the first procedure, surgeons will remove more than three-quarters of the patient's stomach.

And in the second procedure, his remaining stomach will be partially blocked, helping to give a feeling of fullness. Mr Juan Pedro would also undergo intestinal surgery, his doctor said.

Dr Castaneda wants him to lose 59 kg in the first six months, which alone will reduce his risk of obesity-related cancer by 52 per cent.

The 32-year-old has a good chance of losing half his body weight by about six months after his first surgery, according to his medical team.

"Slowly but surely, I'll get there," he told reporters.