This is a story looking at a data analysis of a large Danish health registry, in which researchers determined that the BMI (body-mass index) “associated with the lowest risk of death has increased … from 23.7, in the ‘normal’ weight category, to 27, which is deemed ‘overweight.'”
The story would have been much stronger if it had included that this type of finding is not new, and has been written about before and is known as the “obesity paradox.” This was an opportunity to rise above some of the criticisms leveled at journalists for simplified coverage on this topic.
This matters because much of the world has been gaining weight in recent decades. How that might affect individuals’ likelihood of dying prematurely is important to many of us.
While the benefits–increased survival–were discussed, they were quantified in a confusing way. For example, the story says that the risk of death for obese people, defined as having a BMI of at least 30, declined “to the point that it was on a par with some people of so-called ‘normal’ weight. So being fatter, at least a bit, may be healthier.”
It is hard to figure out what that means. It would have been more helpful if the story had quantified the death rates of the various groups discussed–that way readers would have a clearer sense of how likely it is that the extra weight will help you “cheat death.”
The story did a good job describing why some people with low BMI might be at higher risk of dying– i.e., they may be suffering from cancer or another disease that could cause weight loss.
We’re giving this rating a barely-passing Satisfactory. The story points out some limitations, but doesn’t get into the larger issue of this being an observational study.
And some of the language, including the headline, suggests that there could be a cause-and-effect relationship– something this type of study isn’t designed to prove.
It didn’t mention the many factors — beyond age, sex, smoking, cancer and heart disease — that could confound the relationship between BMI and mortality in this type of study. There was an extensive discussion of those factors the last time this type of research made the rounds, and the same concerns apply here.
The story noted that the number of people who are overweight or obese has been increasing in many countries in recent decades–an assertion that can be backed up with data–and did not overstate the case.
There were no apparent conflicts of interest. However, only one researcher was quoted, but nobody else independent of the work.
The biggest gap in this story is that it didn’t put this study in context with older studies raising the same issue. With no mention of past research, it makes it sound like a novel finding. But it’s not: On the JAMA study page, over on the right-hand side of the page are links to “related” research, including a large meta-analysis on the topic.
The story does not appear to rely on a news release.