By Lisa Rapaport

Residents of Mexico City who are obese may be more likely to die prematurely than their slimmer counterparts, especially if they have lots of extra fat around their midsections, a new study suggests.

Obesity has long been linked to an increased risk of an early death for people from different racial and ethnic groups, but some previous studies have not found this to be the case in Hispanic populations, researchers note in the Annals of Internal Medicine.

“However, the studies on which those claims are based had not accounted for the fact that, while obesity makes diabetes and several other chronic diseases more common, these diseases may then result in substantial weight loss, thereby hiding the reason why those diseases arose in the first place,” said Jonathan Emberson, a senior author of the current study and a researcher at the University of Oxford in the U.K.

In the current analysis, researchers examined data on 115,400 adults, ages 35 to 75, who were free of any chronic illnesses that might be caused by obesity or contribute to weight loss. Participants were typically overweight, with an average body mass index (BMI) of 28 when they joined the study.

To put that in perspective, a person who’s 5 feet 6 inches tall (168 cm) and weighs 175 lb (about 79 kg) would have a BMI of 28.

Researchers followed participants for at least five years and as long as 14 years. Every extra 5 units of BMI at the start of the study was associated with a 30% higher risk of dying from all causes during follow-up.

The connection between BMI and premature death was more pronounced for younger participants.

Each 5-unit increase in baseline BMI was tied to a 40% greater risk of death from all causes during the study for people 40 to 60 years old at the start. Participants who were 60 to 74 years old at the start, however, had only a 24% higher risk of death during the study with each 5-unit increase in baseline BMI.

Compared to a BMI of 25 at age 40, life expectancy would be shortened by 3 years for people with a BMI of 30 and by about a decade with a BMI of 40, researchers calculated.

Waist circumference, or the amount of fat people carry around their midsection, also appeared to impact the risk of premature death.

Compared to people with a waist of just 80 centimeters (cm), or about 31 inches, individuals 40 to 70 years old with a waist circumference of about 100 cm (about 39 inches) were roughly 50% more likely to die during the study, and the mortality risk for people with a waist circumference over 120 cm (about 47 inches) were more than twice as likely to die.

Dr. Jose Medina-Inojosa, a cardiologist at the Mayo Clinic in Rochester, Minnesota, who was not involved in the study, told Reuters Health by email, ” Having a big belly is likely the consequence of inactivity, spending too much time sitting down , a diet that is high in processed foods and sugars. The waist measurements used in this study are also a marker of increased visceral fat (fat around your organs) that has been linked to increased inflammatory markers and incidence of cardiovascular diseases.”

One limitation of the study is that researchers lacked data on what proportion of patients had diabetes, which is common among people with obesity and also common in Mexico, the study team notes.

Even so, the results suggest that Hispanic people may not be spared the mortality risk associated with obesity and excessive belly fat, Emberson said.

“Overweight and obesity are major causes of death in Hispanic populations, just as they are in non-Hispanic populations in America and Europe,” Emberson said. “Combining a good diet with regular exercise is the best way to maintain a healthy weight.”

SOURCE: Annals of Internal Medicine, online August 12, 2019.