The scale is a liar.
Not intentionally, of course. But the number staring back at you each morning is one of the most misleading pieces of health data you'll encounter. It can stay exactly the same while your body transforms. It can spike or drop several pounds based on nothing more than water weight and what you ate for dinner. And it tells you absolutely nothing about whether you're actually getting healthier.
Dr. Abbie Smith-Ryan knows this better than anyone. As a professor of exercise and sport science at the University of North Carolina and one of the leading body composition researchers in the country, she's spent her career measuring what our bodies are actually made of—and why that matters far more than the number on a scale.
In this conversation between Thrive's Chief Medical Officer Dr. Jared Pelo and Dr. Abbie Smith-Ryan, we break down why body composition matters more than weight, what DEXA scans reveal, and how to actually improve your health.
Dr. Smith-Ryan experienced this firsthand. During a physique competition earlier in her career, her weight stayed exactly the same despite losing fat and gaining muscle. Same weight. Completely different body.
Water weight is the main culprit behind the scale's unreliability. Carbohydrates stored in your muscles hold water—so eating a big meal can make the scale jump up, while skipping meals can make it drop, neither of which reflects actual fat or muscle changes.
Beyond that, weight should change over time. "When I was running collegiately, my body weight was in the low 120s," Dr. Smith-Ryan shares. "That's not a healthy weight for me now in my 40s with kids and a full-time job. My body weight now is in the 140s—that's 20 pounds heavier, and I'm actually much healthier."
Body composition breaks down what your body is made of: muscle mass, fat mass (including dangerous visceral fat around organs), bone density, muscle quality, and where you store fat and muscle.
"You cannot look at a person and know whether they're healthy or not," Dr. Smith-Ryan says. "Even if they have excess fat or are very lean, that does not tell us about their health. The only way to know is to look inside the body."
She points to bodybuilders who look lean but are metabolically unhealthy, and individuals with obesity who are cardiovascularly healthy. The difference is invisible from the outside.
DEXA (Dual-Energy X-ray Absorptiometry) scans are the most accurate way to measure body composition. Unlike scales or handheld devices, DEXA can detect changes as small as half a pound of muscle or fat and shows exactly where fat is stored in your body.
"DEXA allows us to look at regional body composition—how much muscle is in your arms, legs, and trunk. Most importantly, we can measure visceral adipose tissue, the fat around your organs, which is one of the most important health markers," Dr. Smith-Ryan explains.
Visceral fat is directly tied to metabolic disease, cardiovascular disease, and inflammation. You can't see it from the outside, and you can't measure it with a scale.
Fat-Free Mass Index and Appendicular Lean Mass Index assess how much muscle you have relative to your height.
"These metrics are really important because they tell us about muscle mass in a way that accounts for body size," Dr. Smith-Ryan explains.
Muscle is metabolically active tissue that improves insulin sensitivity, supports bone health, and helps protects against injury. It also declines significantly with age—but here's the good news: "I've seen 80-year-old men and women put on muscle and build bone. Your body will adapt at any age,” she says.
This is the dangerous fat stored deep in your abdomen, wrapped around your organs. Unlike subcutaneous fat (the fat you can pinch), visceral fat releases inflammatory compounds that increase your risk of heart disease and diabetes. You can have a normal weight or BMI and still have high visceral fat—the only way to measure it is with a DEXA scan.
"We hear so much about body fat percentage in the media, and I think it's because it's an aesthetic thing," Dr. Smith-Ryan says. "But honestly, I don't focus on it as much. When we focus on the right things—muscle, metabolic health—body composition changes naturally. Clothes fit better. You feel better."
Understanding what you're made of is only half the battle. The strategies that actually work are simple, sustainable, and don't require perfection.
"Muscle is metabolically active tissue. It's protective. And it declines significantly with age if you don't maintain it," Dr. Smith-Ryan explains. The good news? You don't need hours in the gym.
"It's about short, consistent sessions. Targeting muscle a few times per week will have the biggest impact over time.”
"I build my plate around a protein and a green," Dr. Smith-Ryan says. "I prioritize vegetables and add in fruit. I don't usually need to encourage people to add more carbohydrates—they're delicious and easy to come by."
Her philosophy is straightforward: start with what your body needs most—protein for muscle and vegetables for nutrients. Everything else fits around that foundation.
"If I'm going to have pizza, I'll also add a salad and get a chicken breast on top. It's more food, but I'm still having my pizza—I'm just also having that green and protein," she says.
The key? Consistency, not perfection. "Sometimes I still just eat pizza for a meal, and that's okay," Dr. Pelo adds. "But most of the time, I try to build around a protein and include fruits and vegetables." This is why Thrive's medical weight loss programs focus on preserving muscle while losing fat—not just the number on the scale.
When you can see what's actually happening inside your body, you can make informed decisions about your health—not just guesses based on a scale.
"I wish everyone had their body composition measured," Dr. Smith-Ryan says. "I do mine every six to nine months. It's really helpful to see how my lifestyle choices have impacted things, and I know how to change it."
Body composition data isn't about judgment—it's about empowerment. "No matter where you are, what age you are, what life stage, your body will adapt," she says. "It is very satisfying to be able to have control over something. And it's not always about fat. There's a lot of strength and muscle and bone health that we can target and change."
Body composition reveals what the scale never will:
At Thrive Wellness, we use DEXA scanning and advanced body composition analysis to help you understand what you're actually made of—and create personalized plans to optimize it. Health isn't about a number on a scale. It's about what's happening beneath the surface.