What AI Body Scans Can (and Can’t) Tell You.
We’re experiencing a veritable thinness epidemic. Even if it doesn’t mean anything to you that celebrities are getting thinner, notice how ads for various weight-loss products are becoming increasingly ubiquitous. When I look around, this onslaught isn’t limited to GLP-1 ads. What’s really caught my attention lately is how I—a fitness journalist who, by the way, is quite thin—constantly receive targeted ads for various types of “AI-powered body scans.” These services take several different forms (which I’ll discuss below), but they all try to sell the same idea: it turns out I don’t know enough about my body. It turns out I need to know my body fat percentage, muscle mass, visceral fat, and, of course, my ” biological age .”
Before I detail what these AI-powered devices can (and can’t) show, please know that this isn’t a criticism of the AI tools radiologists use to detect cancer from CT scans. I’m focusing on the false advertising they offer consumers like me, people who are naturally drawn to the best tools to understand every detail about their bodies. But before making health decisions based on numbers on a screen, I need to consider the gap between what these tools promise and what they actually deliver.
What exactly are AI body scans?
Body composition scanning is nothing new, but the use of artificial intelligence is giving the market a new perspective. The term “AI-powered body scanning” encompasses a wide range of technologies, from clinical DEXA machines used in research hospitals to apps that claim to estimate body fat percentage from selfies.
At the higher end of the spectrum is DEXA (dual-energy X-ray absorptiometry) scanning. Originally developed to measure bone density, DEXA uses two low-dose X-ray beams to precisely distinguish between bone, fat, and muscle tissue. It can identify visceral fat (the dangerous type of fat that accumulates around organs), regional fat distribution, and bone density. A single session can cost between $40 and $300, depending on location and insurance coverage. For example, companies like BodySpec have built their business on making DEXA more accessible, performing approximately a thousand scans per day and creating what they claim is “the world’s largest proprietary DEXA dataset.”
Below DEXA on the accuracy ladder is bioelectrical impedance analysis (BIA). BIA is the technology behind most ” smart scales ,” body composition machines at gyms, and many of the AI-powered consumer scanners that constantly show me ads. BIA works by passing a small electrical current through the body and measuring its conduction. Fat resists the current; muscle tissue (mostly water) conducts it well. Based on this resistance, the device estimates body composition.
Then, at the very bottom of the technical hierarchy, are phone camera apps. Converting a two-dimensional image into an estimate of body fat percentage or visceral fat requires, at best, very high guesses. These apps can be useful as very rough tools for assessing body condition, but the same can be said for photography.
One more note about “artificial intelligence” in this context.
Again, it’s worth clarifying what exactly AI does in most of these products, because, as always, the word can mean many things. More advanced DEXA-based services use AI to process and contextualize large data sets, helping users understand their results relative to relevant populations, identifying trends over time, and personalizing recommendations. For example, BodySpec describes using AI to create a kind of institutional memory for each client within its scanning service, integrating medical history and personal context to ensure consultations feel personalized across the organization.
In consumer devices, “artificial intelligence” most often refers to an algorithm trained on a dataset to estimate body composition. However, the effectiveness of AI depends on the quality of the underlying measurements, and these measurements can be inherently inaccurate.
What AI body scans can’t reveal
Let’s consider where marketing diverges from medicine, and where some doubts are warranted. A body composition scan can’t tell you about your insulin sensitivity, inflammation, thyroid function, cortisol levels, or dozens of other physiological variables that determine your actual metabolic health. Two people can have identical DEXA results (same muscle mass, same body fat percentage, same visceral fat levels), but one may have prediabetes and the other may not.
“I’ve had two people with similar scan results but completely different metabolic states after blood work,” says Dr. Raymond Douglas, a board-certified oculoplastic surgeon and professor at Cedars-Sinai Hospital in Los Angeles. “And if you’re making lifestyle decisions based solely on scan results, you may be addressing the wrong issue.”
Moreover, this interpretation of scan results assumes the readings were initially accurate, which isn’t always the case. “I have years of experience working with patients who have high muscle mass readings, but it’s simply water retention,” says Dr. Alexander Acosta. “If you’re retaining more water, say, after a salty meal or menstruation, the device will likely show a 5% increase in muscle mass.” This is especially true for devices that use bioimpedance analysis, like the smart scales you see at the gym. Your hydration status, which fluctuates throughout the day depending on exercise, diet, and your hormonal cycle, will skew the results.
Perhaps no other feature of these AI scanners is advertised as aggressively as ” biological age .” The marketing ploy is entirely justified: what if you learned that on paper, your body is actually half your age? Unsurprisingly, this figure evokes either relief or horror, and it’s often what motivates a purchase.
Biological age is typically calculated by an algorithm that compares your data to population averages, and these averages are limited. “In my experience, algorithms don’t take into account your genetic predisposition and inherited metabolism. A computer might tell a 30-year-old that they have a 50-year-old heart due to stress,” says Acosta. “I’ve actually seen those numbers change by five years after a bad night’s sleep.” A number that fluctuates by five years based on a single night’s sleep isn’t something to obsess over, if you ask me.
What are body scans actually useful for?
One way to approach all of this is to view the body scan as a tool for tracking trends over time, rather than expecting a single session to dramatically change your life. “Increased muscle mass, decreased visceral fat—those are things worth noting,” says Douglas. “Most people make the mistake of treating a single session as a full-fledged medical examination.”
By scanning under the same conditions every few months, you can gain a lot of useful information from the observed patterns. Are you gaining muscle mass while losing fat? Is your visceral fat increasing despite a stable weight? Body composition scanning, performed repeatedly, unlike traditional bathroom scales, can help answer these questions.
“Dexamic densitometry (DEXA) provides a much clearer picture of what’s really going on in your body by measuring body fat percentage by region, muscle mass, bone density, and visceral fat,” says Elaine Shi, CEO and co-founder of BodySpec. “This allows us to eliminate guesswork based on indirect measures like BMI—which are outdated and don’t reflect the situation in different populations—and make decisions based on clinically sound data.” For example, Shi says that people taking GLP-1 supplements for weight loss may lose a significant portion of their muscle mass rather than fat, which could indicate a metabolic issue that wouldn’t be apparent on a regular weigh-in.
How to use these tools without being fooled by them
If you plan to use DEXA, do so over several months. Multiple scans performed under the same conditions (same time of day, same hydration level, same proximity to the training site) may reveal patterns worth paying attention to. If you plan to use BIA devices, be aware that the readings may be inaccurate. Don’t scan after eating salty foods, after intense exercise, or during hormonal fluctuations; don’t expect accuracy. If you’re interested in inflammatory markers, fasting glucose, insulin, lipid profile, or thyroid function, a body composition assessment is not a substitute for a blood test.
“Consider the scan as an awareness tool, and then combine it with blood tests, blood inflammatory markers, and lifestyle to draw conclusions,” says Douglas. Biological age measurements should also be treated with particular skepticism. A single number derived from comparing your data to the population average for a given day is not a meaningful medical conclusion. And when you see an ad for a phone camera app that claims to measure visceral fat using AI, ask what exactly is being measured. If there’s no good answer (and there won’t be one in a 2D image), the so-called AI has nothing to work with.
Result
The transition from BMI to actual body composition measurements holds promise for many people. If your doctor refers you for a DEXA scan to assess your bone density and you’re interested in other body composition data, consider the scan results as part of a broader trend over time. A body composition score can be a great starting point, but you should still have the results interpreted by a healthcare professional.
Ultimately, quackery will always thrive in the health and wellness industry. Today, every quack knows how to slap the authoritative label “AI-powered” onto flawed products. Before spending hundreds of dollars on a body scan (or wasting time and energy on a mobile app), consider the limitations of these methods and honestly assess what exactly you’re trying to learn. A scan that can’t distinguish muscle from water retention, whose biological age indicator changes by five years with poor sleep, and whose readings depend on what you ate for lunch, may not give you the answers you’re looking for about your body.