A new study finds that being overweight, as defined by the BMI scale, is not associated with increased mortality when considered separately from other health problems.
Also known as BMI, this calculator measures a person’s body fat based on height and weight. The BMI scale currently in use classifies the adult population into varying degrees of body fat..
aAn adult is considered “overweight” if their BMI is within the following range: According to the US Centers for Disease Control and Prevention, a “healthy” or “normal” weight is defined as a BMI between 18.5 and 24.9. A BMI of 30 or higher is considered obese.
“The real message of this study is that overweight as defined by BMI is a poor indicator of mortality risk, BMI in general is a poor indicator of health risk, and waist circumference and other measures of obesity “It should be supplemented with information such as,” said the study’s lead author Ayush Visalia, PhD, an internal medicine residency at Rutgers Robert Wood Johnson School of Medicine in New Brunswick, New Jersey.
But limitations in the study make it difficult to determine whether the results were due to BMI or other factors, according to experts not involved in the new study.
“The use of the word ‘overweight’ here is misleading as it excludes people with a BMI greater than 30. In general terms, ‘overweight’ usually means above ‘normal’. It will be interpreted as a person with weight, and obese patients will also be included,” he said. Doctor. Baptiste Roulin, a lecturer in medical statistics at University College London, said in a statement.
“In this paper, we found a clear association between BMI and mortality before and after adjusting for risk factors,” said Roulin, who was not involved in the study.
In addition, Dr. Robert H. Schmerling, senior faculty editor at Harvard Health Publishing, a subsidiary of the Harvard Medical School in Boston, said that observational studies show only association, not causation. said it can.
“They looked at mortality, but there are other important outcomes that they didn’t look at, such as quality of life and the development of new comorbidities such as new cases of diabetes and heart disease.” Schmerling said. He was not involved in research.
In the new study, published Wednesday in the journal PLOS ONE, the researchers found that 550,000 non-pregnant Americans aged 20 and older from the 1999-2018 National Health Interview Survey and the 2019 U.S. National Death Index We analyzed data collected from more than 4,000 people.
Dr. Visalia and co-author Noriko Setoguchi, Ph.D., professor of medicine and epidemiology at the Rutgers Robert Wood Johnson School of Medicine and the Rutgers School of Public Health, then compared BMI levels with the number of deaths that occurred over the next 20 years. .
For most people with a BMI level above 27.5, the risk of death increased from 18% to 108%, according to Visalia, and the risk increased as weight increased in a U-shaped curve.
There was one exception. It’s adults over the age of 65. There was no significant increase in mortality among older adults with a BMI between 22.5 and 34.9. This range includes normal weight, overweight and obese individuals.
“This paper adds nothing new,” said Naveed Satar, professor of cardiovascular and metabolic health at the University of Glasgow, Scotland, who was not involved in the study.
“We know that BMI often follows a U-shaped curve with mortality, but this is because many people at the lower end of the BMI range (especially the elderly) inadvertently lose weight due to illness. because it’s causing them,” Sattar said in a statement.
In older adults, weight loss is often closely associated with the development of dementia, cancer, and anorexia. Previous studies have found that even a 5% weight loss can increase the risk of premature death in adults over the age of 65, especially men.
Experts say being overweight doesn’t lead to early death, but it can increase the risk of chronic disease.
Visalia said the most important findings involved people aged 20 to 65 with a BMI of 24.5 to 27.5 (the lower end of the overweight scale). There was no significant increase in mortality risk.
But Tom Saunders, emeritus professor of nutrition and dietetics at King’s College London, who was not involved in the study, said future disease risk is “probably a more important health indicator than all-cause mortality.” is,” he said.
“The main risk of being overweight (BMI 25-29.9) and moderately obese (BMI 30-35) is a three-fold increased risk of developing cardiovascular disease, kidney failure and diabetes, which contributes to blindness.” he said in a statement.
The study controlled for smoking and various other illnesses associated with early death, but the information was collected only once per study participant. Therefore, the study could not track whether the person later developed conditions that could lead to death, such as high blood pressure or diabetes, a limitation of the study, Visalia said in an email. told CNN.
“They didn’t even look into the cause of death.”
“Additionally, looking at the full picture of the findings, they found that: Increased mortality from obesity — so it’s not that they deny the utility of BMI for all purposes,” he said.
People in the overweight category see their doctors more often, make lifestyle changes such as exercising more, adopting a healthier diet, and suffer from diabetes, heart disease, Schmerling said. , and may be receiving medical care to prevent other comorbidities from developing. .
“Deaths from obesity can be attributed to the development of diseases such as heart disease, but we know that obesity is also a disease in its own right and can independently increase the risk of death. ,” said Dr. Visalia. “The question is how to diagnose obesity, which may not represent a risk.”
In addition to BMI, Visalia said the study also looked at waist circumference, or the widest part of the torso. stomach. The results showed that using waist circumference “changed significantly the association between BMI and all-cause mortality,” he said.
“Within the same BMI group, those with higher waist circumference had a higher risk of death than those with normal waist circumference,” Dr. Visalia said in an email. “In the overweight BMI range (25 to 29.9), the risk of death was 17% to 27% higher in those with higher waist circumferences than in those with lower waist circumferences.”
This type of deep fat that surrounds the organs of the body, often referred to as abdominal or visceral fat, is associated with a 39% higher risk of dementia in older women, heart disease, frailty and early death in both men and women. I’m here.
According to guidelines issued by the American Heart Association in April 2021, measuring your waist circumference should be combined with getting on the scale as part of your health assessment. As is known, abdominal obesity is defined as waist circumference greater than 40 inches (102 centimeters) for men and greater than 35 inches (88 centimeters) for women.
The American Medical Association also recently adopted new guidelines requiring physicians to use more than BMI when assessing an individual’s health.
“BMI is primarily based on data collected from previous generations of non-Hispanic white populations,” the AMA wrote. It “has a significant correlation with fat mass in the general population, but loses predictability when applied to the individual level.”
The use of BMI as a measure of potential health risk may not disappear from clinical practice as it is included in a thorough work-up, but it should not be the only measure, Dr. Visalia said. said.
But the debate over how fat mass is measured doesn’t change what science knows about the effects of excess weight on the body, experts say.
“Other evidence shows that being overweight increases your risk of developing multiple diseases,” said Professor Sutter of the University of Glasgow.
“These conditions have a negative impact on people’s quality of life and well-being,” Sattar said in a statement. “It is these ‘quality of life’ indicators that we need to pay more attention to and, where possible, improve through relevant interventions at multiple stages of life.”
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