[Reading Science] Is It True That Overweight People Live Longer Than Normal?

Rutgers Institute Study in the US
Survey of 500,000 Samples Shows 5-7% Lower Mortality Rate

Medically, a large-scale population survey has proven that overweight individuals, meaning those who are slightly 'chubby,' are actually healthier and live longer than people classified as 'normal.' This study addresses the weaknesses of previous similar research and is expected to solidify the 'common belief' into an established fact.

The American science media outlet NewScientist reported on the 5th (local time) citing a large-scale population survey conducted by the Rutgers Health Institute in New Jersey, USA. While it is clear that obesity is detrimental to health, the exact threshold at which it becomes a health risk remains unclear. To measure this, the Body Mass Index (BMI), which divides weight by the square of height, is commonly used. The World Health Organization (WHO) established BMI classification criteria in 1997: 18.5?24.9 is considered normal, 25?29.9 overweight, and 30 or above obese.

However, these criteria have been criticized for being somewhat disconnected from actual health and longevity outcomes. Surveys have shown that overweight individuals have a slightly lower mortality rate than those in the normal range. But these studies were conducted long ago, and limitations such as participants becoming slimmer over time and a lack of racial diversity have been pointed out.

How to Reduce Waist Circumference
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To overcome these limitations, the research team tracked the height, weight, and survival rates of 500,000 American adults of diverse races over about 20 years starting from 1999. The results showed that people who were slightly overweight, with a BMI of 25?27.4, had a 5% lower risk of death compared to those in the normal range of 22.5?24.9. Even those who were heavier, just below the obesity threshold with a BMI of 27.5?29.9, fared better, with a 7% lower mortality risk compared to the normal group.

There are criticisms that these findings may be an illusion. Typically, people lose weight when they are ill, and those individuals have a higher likelihood of death. However, the research team accounted for this by excluding individuals who died within two years of data collection, yet the same pattern persisted.

Scientists have shown varied reactions to these findings. Ashri Visaria, a researcher on the team, stated, "Studies using demographics and populations may have biases that distort results, so we cannot definitively say that the overweight category defined by WHO is healthier than the normal category." However, she added, "BMI is not an excellent indicator of mortality risk compared to other factors important to health, such as fat distribution."

Catherine Fligal, a researcher at Stanford University, also commented, "The current criteria for overweight and obesity are arbitrary. The human body does not produce neat and perfect numbers on its own; rather, people have been led to prefer numbers between 25 and 30."

In this regard, the American Medical Association recommended in June that its members no longer rely solely on BMI to assess patients' appropriate weight or obesity status but consider waist circumference and other health indicators as well. Roy Taylor, a professor at Newcastle University in the UK, pointed out, "BMI was developed as a method to assess population health and should not be used as a tool for individual health advice."