Visitors to the mountainous city of Chongqing may be surprised at the local people's craze for spicy hotpot and their taste for animals' internal organs.

Chongqing people have recently voted ox stomach the most popular hotpot dish, according to the Chongqing Hotpot Association's new Hotpot Red Book, the first time the city has published such a report.

Lotus root and fried pork are also favorite orders, according to the book, which was released earlier this month.

Boasting both the best and largest number of hotpot restaurants in the country, Chongqing was named "China's hotpot city" by the China Cuisine Association in 2007.

The association said the municipality has about 26,300 hotpot eateries, hiring nearly 500,000 employees.

But the affordable cuisine is getting more expensive. The average cost per person per meal is now about 50 yuan ($8), up from 30 yuan three years ago.

In 2013, the total net profit from such cuisine in Chongqing was an estimated 15 billion yuan with an annual growth of 15 percent.

"I eat hotpot at least twice a week, even in summer," said Li Yan, 37, a small-business owner in Chongqing.

While acknowledging that "it's not too healthy", given hotpot's excessive oil and spices, "Chongqing locals just can't live without it".

Li said he believes the number of hotpot restaurants in Chongqing is much higher than the association claims.

"Only 26,300? No way. There are five hotpot places within 150 meters of my home," Li said.

Traditional Chongqing hotpot uses beef tallow and large quantities of chili and Sichuan peppers.

And it is still the favorite of local diners, although new styles of hotpot, such as beef and mild duck soup, have gained in popularity in recent years.

Although there is no hard evidence on how it originated, many believe that Chongqing hotpot emerged from the porters' cuisine of the late 19th century.

Chongqing is a port city surrounded by the Yangtze and Jialing rivers. In the late 19th century, animals from Sichuan, Guizhou and Yunnan provinces were shipped by water. Good meat was shipped and sold to the upper and middle classes.

The internal organs, including stomach and kidney, were discarded or sold cheaply. Porters picked up or bought the organs and cooked them in a boiling pot with spicy sauce.

During World War II, when Chongqing was the wartime capital, the food gained popularity among people from all around the world.

"Hotpot is our city's signature cuisine with a long history," said Li Dejian, head of the Chongqing Hotpot Association.

To maintain its popularity, "the whole industry needs to upgrade its management and cultivate its culture", he added.

The Hotpot Red Book says that in 2013-14, the Chongqing hotpot industry underwent rapid growth thanks to the chain-store business model and overseas expansion.

In 1995, Little Swan became the first Chongqing hotpot restaurant to open a branch overseas when it set up a hotpot eatery in Seattle.

Now from New York to Dubai, the chain stores of famous local Chongqing hotpot places are all over the world.

Last year, the city exported 400 metric tons of packed hotpot soup base to 10 countries and regions, including the United States, Australia and Southeast Asia.