"Can you give me another soft drink to quickly wash down the fifth taco? And the bill please," Martinez, a 42-year-old accountant weighing in at 140 kilograms (309 pounds), asked the cook.
The damage for his wallet is relatively light: 40 pesos ($3) for five meat tortillas and 18 pesos ($1.4) for two sodas.
But Mexico is paying a heavy price for its diet, giving it the dubious distinction of being the world's top consumer of sodas and home of the world's second most obese population after its giant northern neighbor, the United States.
Latin America's second biggest economy after Brazil has lived through lean times in the past, with a damaging peso crisis in 1994 and the global financial debacle in 2009. But it has enjoyed periods of growth.
And Alejandro Calvillo, director of the Consumer Power non-governmental organization, said the free trade pacts credited with helping Mexico's economy grow have stuffed the country with less healthy foods.
"There has been a change in eating habits that has sharply increased in the past 20 years, with a bigger infiltration of the processed foods industry" like bubbly soft drinks," Calvillo, whose NGO lobbies for the regulation of such foods, told AFP.
With trade pacts, Mexico has "surrendered to the commercial values of transnational companies that displaced the traditional Mexican diet," he said, blaming also the "relentless" advertising for such products.
Mexico's obesity rate soared from 9.5 percent in 1988 to 32 percent last year in the nation of 112 million people, according to the National Medical Academy. And a staggering 70 percent of the population is overweight -- even though almost half the population lives in poverty.
Mexico guzzles down 163 liters (43 gallons) of soda per capita per year, according to a Yale University study.
The country accounts for 22,000 of the 180,000 annual deaths worldwide associated with sugary drink consumption, a Harvard University study found.
This makes sodas, which come in cola, grape, orange and lemon flavors, a bigger killer than the nation's drug war, which left 10,000 people dead last year.
In late 2012, a bill was introduced in Mexico's Congress to impose a tax on sweet fizzy drinks and regulate advertising for them, but the initiatives fizzled out.
Historically, Mexicans have consumed foods derived from corn -- cultivated by their Aztec ancestors -- as well as a wealth of fruits, vegetables and herbs.
But the sidewalks of this oversized city of 20 million people are dotted with taco and sandwich stands selling tortillas or bread stuffed with an array of greasy meats -- from sliced beef to chicken and even pig snout.
Compounding the problem: scarce drinking water in impoverished communities drives people to consume soft drinks, Yuritzin Flores of the Oxfam international charity group told AFP.
Given the choice between bottled water or a can of soda, "people prefer the drink that gives them more energy and status," Flores said.
Several factors contribute to making a nation obese, including genes, but bad habits adopted by modern societies are mostly to blame, said David Garner, founder of the US-based River Centre Clinic, which treats eating disorders.
"It's due to the fact that society is changing rapidly and what is happening is that food is always available and food that is high in fat and sugar is available," Garner said.
"We know that soda drinks, whether they're diet or regular, they contribute to obesity and heart disease.
"But we don't in any way try to influence this," he added, noting that the soft drink lobby is "extremely powerful."
The Mexican government recently announced it would implement a strategy to combat obesity, without providing much details.
The country's weight problem is becoming a heavy burden on the overstretched public health system, estimated by itself to cost the country $11.7 billion by 2017.
The most common reasons for hospitalizations in Mexico are heart attacks, high blood pressure and diabetes, a disease that affects 14 percent of the population and kills 80,000 people per year.
To deal with the problem, several clinics offer free and cheap gastric bypass surgeries, a procedure that reduces the size of the stomach.
"The surgery does not solve the problem. It's more like an expensive Band-Aid," Garner said.
But Leticia Bautista, a psychologist at the National Autonomous University of Mexico, said the surgery "is a life opportunity" for the obese.
Ofelia Montiel, 52, ballooned to 100 kilograms (220 pounds) in her short, 1.50-meter (just under five-foot) tall frame after consuming three liters of Coca-Cola per day.
More than a year ago, she underwent gastric bypass surgery and has no regrets, even though she gets full very easily these days.
"I still drink Coke because it makes me belch, and then I can eat more food," said the retiree, who now weighs 50 kilograms (110 pounds).