Take a drive around certain neighborhoods in Los Angeles and you may spot as many signs advertising body scans as burger joints. Or maybe you’ve seen the ads on TV or the internet: “Protect your health! Get a body scan now!” 

Are whole-body CT scans really able to do that – and what are the risks? And are DEXA scans a good way to check on your body composition?

While technologies vary, most of these high-tech checkups use computed tomography (CT) scans to examine your entire body or specific parts, such as the heart and lungs, to try to catch dangerous diseases in earlier, more curable stages.

During the 15- or 20-minute scan, you lie inside a doughnut-shaped machine as an imaging device rotates around you, transmitting radiation. The technique combines multiple X-ray images and, with the aid of a computer, produces cross-sectional views of your body. By examining the views, a doctor can look for early signs of abnormalities.

The scans aren’t cheap – whole-body scans run anywhere from $500 to $1,000 per scan and usually aren’t reimbursed by insurance. And the question of how helpful these scans really are is a matter of debate among medical experts.

Advocates promote scans as a smart part of a routine physical exam. But if you’re healthy, with no worrisome symptoms, a scan is usually not warranted, says Arl Van Moore, MD, a radiologist and clinical assistant professor of radiology at Duke University Medical Center in Durham, NC, who is also a spokesman for the American College of Radiology (ACR).

According to the ACR’s official position, there’s not enough evidence to recommend scans for those with no symptoms or family history suggesting disease. But Van Moore sees a possible exception. “There may be a benefit to people at high risk of lung cancers, such as current smokers or those with a long history of smoking,” he says. 

For healthy people, the scans may cause undue worry – for instance, by finding something that turns out to be benign. Plus, the amount of radiation exposure, especially with frequent scans, is another concern. If scans are done too often, the radiation exposure may actually increase the number of cancer cases over the long term, according to a 2004 report in the journal Radiology.

The American College of Preventive Medicine says that whole-body scans “aren’t very good at finding cancer in people without symptoms” and that the radiation you get from these scans can increase your risk of cancer.

Before scheduling a body scan, talk to your doctor about your overall health risks and how a scan may or may not help you. In particular, ask yourself:

• What’s your history? Do you have a personal or family history of lung disease, heart disease, or specific cancers?
• Did you inhale? Are you a longtime smoker?
• If so, how long? Even if you’ve quit smoking, for how many years were you an active smoker?

This is a different type of scan, called DEXA (dual energy X-ray absorptiometry). You might have heard of DEXA scans to check on bone density to see if you have osteoporosis or osteopenia. It uses low-level X-rays to check on your body composition, like how much body fat you have and where it is in your body. 

There are various ways to measure your body fat. Experts have told WebMD in the past that DEXA scanning is a “very good technique” and “one of the most accurate methods out there.” And researchers have called it the “gold standard” for checking on body composition – specifically, for bone, fat, and muscle. But it’s not covered by insurance, unless you’re getting a DEXA scan to screen for bone density. The cost of a DEXA scan varies, starting around $75 in some cases.