The format of this story — with its hepful “Ache, Claim, Verdict” structure — suggests we are going to be treated to a no-nonsense examination of the evidence supporting dual-energy X-ray absorptiometry, or DXA, for whole body scans to determine an individual’s body composition in terms of fat, bone and muscle. However, the story doesn’t deliver much more than a superficial look at the technology and is lacking in critical perspective. The story concludes that DXA is much more accurate than body mass index (BMI) at calculating someone’s body composition, but doesn’t give readers much information on why this may be important to their health. It focuses on the question of how often one should get scanned, and never challenges the assumption that one needs to get scanned at all. It doesn’t mention that there appears to be no data to show that those who use these scans have any better outcomes than those who do not.
We live in a body-conscious society. It’s not clear precisely how much money people in the United States spend on weight loss. U.S. News, for example, reported in 2013 that we spend more than $60 billion a year on weight loss. A year earlier, ABC News pegged it at $20 billion. Regardless of which figure is closer to the mark, the weight loss industry is a juggernaut. And that doesn’t even get into the fitness industry focused on helping us have bigger muscles or more toned bodies. In short, people are extremely interested in losing fat and gaining muscle — and DXA appears to be a tool aimed at, to paraphrase this story, taking the guesswork out of figuring out how well you’re doing. It is, perhaps, inevitable that news outlets will cover this tool and its effectiveness. But these stories should also highlight how and whether they can give people insight into any potential medical problems — or whether it’s primarily a pricey tool for indulging our interest in our own bodies.
The story notes that a whole-body DXA scan costs “$45 to $350 or more” and is generally not covered by insurance. While readers can do the math, it would have been very useful for the story to point out what the costs of scanning at the intervals suggested (up to every 3 months) would amount to over time.
The story notes that some DXA scanners “estimate how much visceral fat you have, a measure that can help predict risk for diabetes and cardiovascular disease.” It also states that scans show “the amount of fat and lean tissue in each body part, such as the right arm or left leg—information that can be helpful for athletes to see if an injured limb is regaining muscle.” However, these claims are not quantified. How much different might one’s risk for diabetes or cardiovasular disease be on a DXA scan vs. traditional body composition measures? How much faster might one recover from an injury using DXA monitoring? To its credit, the story does note that one study found that 18.5% of women with a normal BMI had excess fat when measured using a DXA scan — “making them ‘skinny fat.'” But readers aren’t told what “skinny fat” means — does it have health implications? Does it increase risk and by how much? More quantification here would have helped readers judge the value of this tool.
The story gets credit for noting that DXA scans involve radiation, and for explaining exactly how much radiation one may be exposed to during a scan. However, that information could have been placed in a more health-relevant context. The DXA scan, the story says, exposes someone to “about the same as one day of background radiation” and compares the dose to chest x-rays and mammograms. The story would have have stronger if it had explained whether that means low risk or high. A few more details would have been helpful here.
This is Not Satisfactory for a simple reason: there is nothing presented to show that measuring body composition with a scan vs. other ways leads to any improved outcomes, whether intermediate or long term or whether we’re talking about weight loss, building muscle mass, increasing athletic performance, or preventing heart disease. This is a really important issue that was neglected by the coverage. If readers are going to be tempted to get an expensive scan over using a bathroom scale and a mirror, they should have some assurance that it will actually lead to better results — or at least be warned if we don’t have enough evidence to judge. [Editor’s note: On Twitter, well-known cardiologist Dr. Eric Topol, editor of Medscape, greeted the story with this comment: “Just what we don’t need: a high tech, whole body scan to show loss of fat.”]
It’s arguable that this story contributes to concentrating on appearance rather than health, and may get people with a normal BMI worrying about whether they are “skinny fat” — without offering any evidence that this is a real problem. However, since we didn’t see any egregious exaggerations of the obesity problem, we’ll give the benefit of the doubt.
There are multiple sources here with conflicts of interest, but they are all clearly identified — and the story includes at least two sources who appear to have no conflict of interest. However, it would not have been difficult to find someone with a much more skeptical take on this technology, and we wish that perspective had been included.
The story addresses four other techniques used for assessing body fat: BMI, water weighing, bioimpedance and pinching folded skin with calipers. The story would’ve been more useful had it mentioned that there appear to be no comparative effectiveness studies on long term outcomes using these different methods.
Tough call here. The story says that DXA scans are “available at a growing number of spas, hospitals and doctor’s offices.” But the statement comes from a company representative. What does “growing number” mean? Are you likely to be able to find this outside of posh resorts and major cities?
DXA scans are clearly distinct from other techniques for assessing body composition, but it’s not new. Researchers have been writing about using DXA scans to assess body composition since the early 1990s. The story gives a sense of why this is newsworthy now when it says, “A DXA scan (pronounced dexa) is commonly used to measure bone density, but recently has been increasingly used to measure body composition.” We’ll call that good enough for a Satisfactory rating.
There is enough original reporting here that we can be sure the story wasn’t based entirely on a news release.