BOULDER, Colo. — Although carrying too much weight can increase the risk of high blood pressure and heart disease, few studies actually say simply being a little overweight can lead to premature death. However, a new study is changing everything, finding that obesity significantly increases a person’s risk of death. A researcher from CU Boulder warns that obesity raises a person’s risk of death by anywhere from 22 to a staggering 91 percent.
Moreover, the new analysis of nearly 18,000 people finds scientists may be looking at body mass index (BMI) all wrong. The study author says this go-to measure of weight and fitness can lead to scientific bias and can actually provide a misleading picture of someone’s health. In the new study, the researcher found that one in six U.S. deaths have a connection to excess weight or obesity.
“Existing studies have likely underestimated the mortality consequences of living in a country where cheap, unhealthy food has grown increasingly accessible, and sedentary lifestyles have become the norm,” says study author Ryan Masters, an associate professor of sociology at CU Boulder, in a university release.
“This study and others are beginning to expose the true toll of this public health crisis.”
BMI thinks Tom Cruise is obese!
Masters notes that there is currently an “obesity paradox” when it comes to studying weight and longevity. This U-shaped curve shows that those in the “overweight” category (BMI 25–30) have the lowest risk of death. Meanwhile, previous studies say those in the “obese” category (BMI 30–35) have little to no increased risk of death in comparison to people in the “healthy” category (18.5–25).
“The conventional wisdom is that elevated BMI generally does not raise mortality risk until you get to very high levels, and that there are actually some survival benefits to being overweight,” Masters explains. “I have been suspicious of these claims.”
BMI is a measurement which comes from comparing weight and height only. It doesn’t account for various body type differences that people have, such as a shorter man or woman who is extremely fit and muscular and therefore weighs more.
“It’s a reflection of stature at a point in time. That’s it,” Masters says, citing actor Tom Cruise as an example.
At one point, the action star was an extremely muscular 201 pounds, despite only standing 5 feet, 7 inches tall. According to BMI, that puts the “Top Gun: Maverick” star in the “obese” category.
“It isn’t fully capturing all of the nuances and different sizes and shapes the body comes in,” Masters continues.
How long you’re obese matters the most
In this new study of weight’s link to health, Masters examined data from the National Health and Nutrition Examination Survey (NHANES) from 1988 to 2015. This study included information on 17,784 people, 4,468 who died.
One in five in the “healthy” weight category had been overweight or obese at some point over the past decade. Results show that these individuals in particular had a much worse health profile than other participants whose weight remained stable throughout the study.
Interestingly, results also show that carrying excess weight for a lifetime makes someone more likely to develop diseases which cause rapid weight loss. Therefore, if scientists look at BMI data during this time, Masters says it can skew scientific studies.
“I would argue that we have been artificially inflating the mortality risk in the low-BMI category by including those who had been high BMI and had just lost weight recently,” the researcher says.
Additionally, 37 percent of overweight participants and 60 percent of obese individuals had lower BMIs in the decade prior. Those who recently gained weight still had better overall health profiles. Masters says this shows that lifelong obesity is much worse for health than a sudden spike due to overeating. By including people who had a lifetime of low-BMI weight in the high-BMI category, previous studies have been incorrectly making obesity look safer that it really is, Masters explains.
“The health and mortality consequences of high BMI are not like a light switch. There’s an expanding body of work suggesting that the consequences are duration-dependent.”
Mortality risk has a straight-line link to weight
Instead of a U-shaped curve, the study finds a straight upward line linking BMI to a person’s risk of death. Unlike previous studies, the new report finds no risk increase among people in the “underweight” category. While prior studies estimate that two to three percent of U.S. adults die due to high BMI-related causes, this report says the number is actually eight times higher.
“For groups born in the 1970s or 1980s who have lived their whole lives in this obesogenic environment, the prospects of healthy aging into older adulthood does not look good right now,” Masters concludes. “I hope this work can influence higher-level discussions about what we as a society can do about it.”
The study is published in the journal Population Studies.