Study Findings Contradict Common Knowledge About Obesity and Mortality Risk

Overweight or obesity increases the risk of death by 22% to 91%, significantly more than previously thought, but a new study from CU Boulder overestimates the risk of death from being slightly underweight. It may have been

Findings published in the journal on February 9 demographyrefutes the commonly held belief that excess weight increases mortality risk only in extreme cases.

A statistical analysis of about 18,000 people also sheds light on the pitfalls of using body mass index (BMI) to study health status, where the go-to metric can bias findings. provide evidence of. After considering these biases, it is estimated that about 1 in 6 deaths in the United States is related to being overweight or obese.

Existing research may underestimate the mortality impact of living in a country where cheap, unhealthy food is increasingly accessible and sedentary lifestyles are the norm. This study and others are beginning to reveal the true toll of this public health crisis. ”

Ryan Masters, Associate Professor of Sociology, University of Colorado, Boulder

Challenging the Obesity Paradox

heart disease, high blood pressure, diabetes (often Overweight) Few studies have shown higher mortality in groups with higher BMI because of the increased risk of death.

Instead, what some call the “obesity paradox,” most studies show a U-shaped curve. People in the “overweight” category (BMI 25-30) surprisingly have the lowest risk of death. People in the “overweight” category (ages 30-35) are at little or no increased risk compared to the so-called “healthy” category (ages 18.5-25). Also, both being “underweight” (under 18.5) and being extremely obese (over 35) have an increased risk of death.

“The conventional wisdom is that increasing BMI generally does not increase mortality risk until it reaches very high levels, and that being overweight actually has a survival advantage,” he said. Masters, a sociodemographer who has studied it, said: “I doubt these claims.”

He said that BMI, which is often used by doctors and scientists as a health indicator, is based solely on weight and height, and does not take into account differences in body composition or how long a person has been overweight.

“It reflects how tall you are at one point. That’s it,” Masters said, noting that Tom Cruise (5’7″ at one point, very muscular, 201 pounds) had a BMI of 31.5, making him ” obesity” category. “It doesn’t quite capture all the nuances and different sizes and shapes of the body.”

To see what happened when these nuances were considered, Masters looked at the National Health and Nutrition Examination Survey (NHANES) from 1988 to 2015 and found data on 17,784 people, including 4,468 deaths. I checked.

He found that 20% of samples characterized as having a “healthy” weight were in the overweight or obese category 10 years ago. Separately, this group had significantly worse health than those in the weight-stable category.

Masters pointed out that carrying excess weight throughout life can paradoxically lead to illnesses that lead to rapid weight loss. may occur.

“I argue that by including people with high BMI who have recently lost weight, we are artificially inflating the risk of death in the low BMI category.

On the other hand, 37% of those characterized as overweight and 60% of those with obese BMI had a low BMI 10 years ago. Especially those who had just gained weight recently were in good health.

“The effects of high BMI on health and mortality are nothing like a light switch,” Masters said.

By including people in the high BMI category who spent most of their lives at low BMI weight, he said, previous studies made high BMI appear to be a lower risk than it really was.

He also looked at differences in fat distribution within BMI categories and found significant differences in reported health outcomes.

Exposure to public health problems

Taken together, these findings confirm that studies are ‘significantly affected’ by BMI-related biases.

Recalculating the numbers without these biases, he found no U-shape, but a straight upward line where people with lower BMIs (18.5–22.5) had the lowest risk of death.

In contrast to previous studies, this study found no significant increased risk of death in the “underweight” category.

While previous studies estimated that 2-3% of adult deaths in the United States are due to high BMI, his study projects eight times as many victims.

Masters hopes the study will caution scientists to be “very cautious” when drawing conclusions based on BMI. He hopes to draw attention to what he sees as a public health crisis fueled by an unhealthy or “obesity” environment in the United States, rather than a problem to be solved.

“For the group that was born in the 1970s or 1980s and spent their entire lives in such an obese environment, it doesn’t look like there’s much prospect of healthy aging and aging right now,” he said. . “I hope this work can influence higher-level discussions about what we can do as a society.”