Being overweight and obese raises the risk of death by 22 to 91% – far more than previously thought – while the mortality risk of being slightly overweight has likely been overestimated, according to a new study.
- Being overweight and obese increases the risk of death by 22 to 91 percent, which is higher than previous predictions, according to this new study.
- The study challenges the “obesity paradox” that a high BMI generally does not increase mortality risk until it reaches very high levels, and that there are in fact survival benefits of being overweight.
- Re-analyzing the data, people with a low BMI (18.5 to 22.5) have the lowest mortality risk and there is no significant increase in mortality risk for the “underweight” category. .
A recent study from the University of Colorado – Boulder (CU Boulder), published in the journal Demographic Population Studies, challenges the common assumption that being overweight only increases mortality risk in extreme cases. According to its results, overweight and obesity increase the risk of death by 22 to 91%, which is higher than previous predictions.
1 in 6 deaths are linked to overweight or obesity in the United States
Statistical analysis of 18,000 people also highlights the pitfalls of using body mass index (BMI) to study health outcomes, providing evidence that the baseline measure can potentially bias results. After accounting for these biases, it is estimated that approximately 1 in 6 deaths in the United States is related to overweight or obesity.
“Existing studies have likely underestimated the consequences for mortality in a country (the United States) where cheap and unhealthy foods have become increasingly accessible and sedentary lifestyles have become the norm”said study author Ryan Masters, an associate professor of sociology at CU Boulder who has spent his career studying mortality trends, in a communicated. “This study and others are beginning to reveal the true toll of this public health crisis”he adds.
While many studies show that heart disease, high blood pressure, and diabetes (which are often associated with being overweight) increase mortality risk, very few have shown that groups with higher BMIs have higher death rates. students.
The “obesity paradox”, a false belief?
Instead, in what some call the “obesity paradox”, most studies show a U-shaped curve: people in the “overweight” category (BMI 25-30) are surprisingly at risk of lowest mortality. Those in the “obese” category (30-35) have little or no increased risk compared to the so-called “healthy” category (18.5-25). And the “underweight” (under 18.5) and extremely obese people (35 and over) are at greater risk of death. So, according to this popular theory “a high BMI generally doesn’t increase mortality risk until you reach very high levels, and there are in fact survival benefits to being overweight“, explains Professor Masters.
He noted that BMI, which doctors and researchers often use as a measure of health, is based solely on weight and height and doesn’t take into account differences in body composition or how long you’ve been overweight. of somebody : “It’s a reflection of stature at any given time. That’s all. It doesn’t fully capture all the nuances and the different sizes and shapes of the body.” So much so that the American actor Tom Cruise, who has a BMI of 31.5, could thus be placed in the category of “obese”, whereas he obviously is not.
To arrive at his results, Ryan Masters analyzed data from the National Health and Nutrition Survey (NHANES) from 1988 to 2015, examining data from 17,784 Americans, of whom 4,468 died during the period. He found that about 20% of the sample classified as “healthy” weight had been in the overweight or obese category during the previous decade. Aside, this group had a significantly poorer health profile than those in the category whose weight remained stable.
Low BMI: “the risk of mortality has been artificially inflated”
Ryan Masters pointed out that living with excess weight can lead to illnesses which, paradoxically, lead to rapid weight loss. If BMI data is captured during this period, it may distort the study results. “I would say we artificially inflated the mortality risk in the low BMI category by including those who had a high BMI and had just recently lost weight”did he declare.
Meanwhile, 37% of those classified as overweight and 60% of those with a BMI of obese had a lower BMI in the previous decade. In particular, those who had only recently gained weight had better health profiles.
By including people who have spent most of their lives with a low BMI in the high BMI categories, previous studies have inadvertently made a high BMI less risky than it is, according to Professor Masters. When he looked at differences in fat distribution within BMI categories, he also found that the variations made a huge difference in reported health outcomes.
People with a low BMI would have the lowest mortality risk
By recalculating the numbers without these biases, he found not a U-shape but a straight line upwards, with people with a low BMI (18.5 to 22.5) having the lowest mortality risk. Also, unlike previous research, the study found no significant increase in mortality risk for the “underweight” category.
So while previous research estimated that 2-3% of adult deaths in the United States were due to high BMI, his study put the toll eight times higher. Professor Masters hopes his work will inspire researchers to be “extremely careful” when drawing conclusions based on BMI.
