What AI Body Scans Can (and Cannot) Tell You

We are experiencing a veritable epidemic of thinness. Even if seeing celebrities getting thinner doesn’t mean anything to you, notice how the marketing of various weight loss products is becoming more and more ubiquitous. When I look around me, the onslaught doesn’t stop at all the GLP-1 ads. What’s really caught my attention recently is how I, a fitness writer who happens to be quite thin, keep getting targeted ads for different types of “AI body scans.” These services take different forms (which I detail below), but what they’re all trying to sell is the same idea: Apparently, I don’t know enough about my body. Turns out I need to know my body fat percentage, muscle mass, visceral fat and of course, my “biological age“.

Before I explain exactly what these AI body scans can (and can’t) tell you, please know that this is not a takedown of the AI ​​tools radiologists use to detect cancer from a CT scan. What I’m focusing on here is all the false advertising aimed at consumers like me, people naturally drawn to the shiniest tools for understanding every little thing on their body. But before building my health decisions around a number displayed on a screen, I must question the gap between what these tools promise and what they actually deliver.

What exactly are AI body scanners?

Body composition analyzes are nothing new: it’s the AI ​​angle that gives the market a new angle. The term “AI body scan” covers a range of technologies, from clinical-grade DEXA machines used in research hospitals, to apps that claim to estimate your body fat from a selfie.

At the serious end is the DEXA scan (Dual Energy X-ray Absorptiometry). Originally developed to measure bone density, DEXA uses two low-dose X-ray beams to distinguish between bone, fat and lean tissue with true precision. It can identify visceral fat (dangerous fat that accumulates around organs), regional fat distribution and bone density. A single session can cost between $40 and $300, depending on where you go and whether insurance applies. A company like Body specificationfor example, has created companies aimed at making DEXA more accessible, performing around a thousand scans per day and creating what it describes as the “largest proprietary DEXA data set” in the world.

Below DEXA, on the accuracy scale, is “bioelectrical impedance analysis” (BIA). BIA is the technology that powers the most “smart scales“, body composition stations at gyms, and many of those consumer AI scanners that keep targeting me with ads. The BIA works by passing a small electrical current through your body and measuring its movement. Fat resists the electrical current; lean tissue (mostly water) conducts it well. From this resistance, the device estimates body composition.

Next, at the bottom of the technical hierarchy, are the phone’s camera apps. Translating a 2D image into body fat percentage or visceral fat estimate requires assumptions that are generous at best. These apps can be useful as very rudimentary awareness tools, just like a photograph.

Another note on “AI” in this context

Again, it’s worth being specific about what AI actually does in most of these products, because as always, the word can mean many things. In the best DEXA-based services, AI is used to process and contextualize large data sets, helping users understand their results in relation to relevant populations, report trends over time, and personalize recommendations. For example, BodySpec describes using AI to give its scanning service a sort of institutional memory for each client, bringing together medical history and personal context so that consultations are personalized at scale.

In consumer devices, “AI” most often means that an algorithm has been trained on a dataset to estimate body composition. But AI is only as good as the underlying measurement, and those underlying measurements may not be accurate in the first place.

What an AI body scanner can’t tell you

Let’s take a look at where the marketing deviates from the drug and where some skepticism is warranted. A body composition analysis 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 may have identical DEXA results (same muscle mass, same body fat, same visceral fat reading), but one may have pre-diabetes while the other does not.

“I’ve had two people with similar lab results, but very different metabolic health once the labs were checked,” says Dr. Raymond Douglas, a board-certified oculoplastic surgeon and professor at Cedars-Sinai Hospital in Los Angeles. “And if you’re making lifestyle choices based solely on an analysis number, you may be solving the wrong problem.”

Additionally, this type of interpretation of test results assumes that the reading was accurate, which is not always the case. “I have years of experience seeing patients with high muscle values ​​but simply held back by water,” says Dr. Alexander Acosta. “If you’ve retained more water, for example from a salty lunch or your period, the machine will likely report a 5% increase in your muscle mass.” This is particularly relevant for BIA products, like the smart scales you might see at the gym. Your hydration status – which fluctuates throughout the day, depending on exercise, diet, hormonal cycles – distorts the result.

Perhaps no feature of these AI scanners is marketed more aggressively than “biological age“The marketing angle makes sense: What if you discovered that your body is actually half your age on paper? It’s no mystery that this number has the power to inspire either relief or dread, and it often inspires purchases.

Biological age is usually calculated by an algorithm that compares your information to population averages, and these averages are limited. “In my experience, the algorithms don’t take into account your genetic background and your hereditary metabolic rate. The computer can tell a 30-year-old person that they have a 50-year-old heart because of stress,” says Acosta. “I’ve actually seen these numbers change five years after a bad night’s sleep.” A number that varies by five years based on one night’s sleep is not a number worth obsessing over, if you ask me.

What are body scanners actually used for?

One way to approach all of this is to view body scans as a tool for tracking trends over time, rather than expecting your world to be turned upside down after just one session. “The trend of muscle up, visceral fat down: it’s worth paying attention to,” says Douglas. “The mistake most people make is treating a single session like a complete medical checkup.”

If you run scans under consistent conditions every few months, you will be able to glean a lot of useful information from the patterns that appear. Are you gaining lean mass while losing fat? Is your visceral fat increasing despite a stable weight? These are questions that a body composition analysis, performed repeatedly, can help answer in a way that a bathroom scale cannot.

“A DEXA scan provides a much clearer picture of what’s really going on in your body by measuring body fat percentage by area, lean mass, bone density and visceral fat,” says Elaine Shi, CEO and co-founder of BodySpec. “This moves us away from assumptions based on indicators like BMI, which are outdated and do not represent diverse populations, and allows us to make decisions based on clinical-quality information.” For example, Shi says people taking GLP-1 drugs for weight loss may lose a significant proportion of their lean muscle mass rather than their fat mass, which could indicate a metabolic problem that would be invisible on a normal scale.

If you plan to use DEXA, use it for several months. Numerous examinations carried out under constant conditions (same time of day, same state of hydration, same proximity to exercise) could reveal trends that deserve attention. If you are considering using BIA devices, be aware that the readings are noisy. Don’t scan after a salty meal, after strenuous exercise, or during a phase of hormonal flow and expect accuracy. If you are interested in inflammatory markers, fasting blood sugar, insulin, lipid panels, thyroid function, a body composition score is not a substitute for blood tests.

“Think of the analysis as an awareness tool, then combine it with blood tests, blood markers of inflammation, and lifestyle habits to draw conclusions,” says Douglas. You should also be especially skeptical of biological age scores. A single number generated by comparing your data to population averages on a given day does not constitute substantial medical information. And when you see an ad for a phone camera app that claims to measure your visceral fat with AI, ask what the underlying measurement is. If there is no right answer (which a 2D image isn’t), the so-called AI has nothing real to work with.

The essentials

Ditching BMI in favor of an actual measure of body composition holds promise for many people. If your doctor sends you for a DEXA scan to assess your bone density and you’re interested in other information about your body composition along the way, consider your scan results as part of a larger trend over time. Your body composition score can be a great place to start, but you still want a medical professional to make sense of the results.

Ultimately, snake oil will always thrive in the wellness industry. These days, every snake oil salesman knows how to use the term “AI-powered” to add authoritative language to imperfect products. Before spending hundreds of dollars on a body scanner (or wasting your time and energy on a phone app), consider the limitations of these readings and be honest about what exactly you’re trying to find out here. A scan that can’t distinguish between muscle and retained water, whose biological age varies by five years with poor sleep, and whose readings vary depending on what you ate for lunch may not give you the answers you crave about your body.