Dr Hilary Jones discusses UK’s ‘obesity epidemic’ on GMB
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Being overweight or obese has long been cited as a risk factor for multiple health conditions. Carrying excess weight has been linked to type 2 diabetes, heart disease and even cancer, for example. However, a new study has suggested that being overweight can increase your risk of death by between 22 and 91 percent – significantly more than previously believed.
The research, by the University of Colorado at Boulder, also concluded that the mortality risk of being slightly underweight had likely been overestimated.
Published in the journal Population Studies, the findings contradict current belief that excess weight raises mortality risk only in extreme cases.
Study author and associate professor of sociology at CU Boulder, Ryan Masters, said: “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. This study and others are beginning to expose the true toll of this public health crisis.”
Although various previous studies have shown that heart disease, high blood pressure and diabetes (which are often associated with being overweight) elevate mortality risk, very few have shown that groups with a higher body mass index (BMI) have higher death rates.
“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,” Mr Masters said. “I have been suspicious of these claims.”
He noted that BMI, which doctors and scientists often use as a health measure, is based on weight and height only and doesn’t account for differences in body composition or how long a person has been overweight.
Mr Masters explained: “It’s a reflection of stature at a point in time. That’s it. It isn’t fully capturing all of the nuances and different sizes and shapes the body comes in.”
As an example, Hollywood star Tom Cruise (at five feet seven inches and a muscular 201 pounds at one point), had a BMI of 31.5 – putting him in the category of “obese”.
As part of the research, Mr Masters combed the National Health and Nutrition Examination Survey (NHANES) from 1988 to 2015, looking at data from 17,784 people, including 4,468 deaths.
He discovered that a full 20 percent of the sample characterised as “healthy” weight had been in the overweight or obese category in the decade prior.
When set apart, this group had a substantially worse health profile than those in the category whose weight had been stable.
Masters pointed out that a lifetime carrying excess weight can lead to illnesses that, paradoxically, lead to rapid weight loss. If BMI data is captured during this time, it can skew study results.
“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,” he said.
Collectively, the findings confirmed that studies have been “significantly affected” by BMI-related bias.
When re-crunching the numbers without these biases, Mr Masters found not a U-shape but a straight upward line, with those with low BMI (18.5–22.5) having the lowest mortality risk.
Contrary to previous research, the study found no significant mortality risk increases for the “underweight” category.
While previous research estimated two to three percent of all adult deaths in the US were due to high BMI, his study pegs the toll at eight times that.
Mr Masters said he hopes the research will alert scientists to be “extremely cautious” when making conclusions based on BMI. But he also believes the work is vital for addressing what he branded a public health crisis.
He added: “For groups born in the 1970s or 1980s who have lived their whole lives in this obesogenic environment, the prospects of healthy ageing into older adulthood does not look good right now.
“I hope this work can influence higher-level discussions about what we as a society can do about it.”
It is thought one in four adults in the UK are currently obese.
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