Over the last 11 years, we’ve had countless discussions about health metrics.
One of the most common questions we hear is about Body Mass Index (BMI) and its importance.
The truth?
While BMI has some utility, it’s far from the golden standard many believe it to be.
Let’s dive in and uncover why Body Mass Index isn’t the holy grail of health metrics.
How Body Mass Index is Calculated
BMI (Body Mass Index) is calculated by dividing your weight in kilograms by your height in meters squared.
Since we don’t use kilograms in America, multiply your weight in pounds by 703, then divide by your height in inches squared.
According to the standard BMI categories:
- Under 18.5: Underweight
- 18.5-24.9: “Normal” weight
- 25-29.9: Overweight
- 30 and above: Obese
Seems simple enough, right? Unfortunately, this simplicity is exactly what makes BMI problematic.
Shortcomings of BMI
BMI was developed in the 1830s by Belgian mathematician Adolphe Quetelet.
It wasn’t designed to measure individual health, but rather to study population statistics.
Yet somehow, nearly 200 years later, we’re still using this outdated metric to evaluate individual health.
The most glaring problem with BMI is that it doesn’t differentiate between fat mass and lean mass.
For example, we’ve worked with numerous busy professionals who started strength training and gained muscle mass while losing body fat.
Their weight didn’t change, but their body composition improved dramatically.
According to BMI, there was zero improvement.
Then there’s the case of professional athletes.
Many NFL players, Olympic weightlifters, and bodybuilders register as “obese” on the BMI scale despite having low body fat percentages.
LeBron James, with his muscular frame, has a BMI of around 27, placing him in the “overweight” category.
Can you imagine the absurdity of a doctor telling LeBron he’s overweight?
BMI also fails to consider age, gender, or where you carry your fat.
A 65-year-old woman with the same BMI as a 25-year-old man will have vastly different health implications.
Similarly, visceral fat (around organs) poses greater health risks than subcutaneous fat, but BMI treats all fat equally.
Lastly, BMI doesn’t account for ethnic differences.
Studies have shown that health risks associated with specific BMI values vary significantly across different ethnicities.
Why Body Fat is a Better Indicator of Health
While BMI measures your relationship with gravity (weight relative to height), body fat percentage tells you what that weight consists of.
And that’s what actually matters for health.
Higher body fat percentages are associated with increased risks of cardiovascular disease, type 2 diabetes, and certain cancers.
But the relationship between weight and health isn’t always straightforward.
A person with a “normal” BMI but high body fat percentage (sometimes called “skinny fat”) can have worse health markers than someone with an “overweight” BMI but more muscle mass.
The former might appear healthy from the outside but have metabolic issues lurking beneath the surface.
Body fat measurement also allows us to track meaningful progress.
When a client loses 5 pounds of fat but gains 5 pounds of muscle, their weight remains unchanged, but their health and physique improve dramatically.
BMI would miss this entirely.
Why We Use the InBody 570
At No Limits Fitness, we use the InBody 570 because it provides comprehensive body composition data beyond just weight and BMI.
This advanced bioelectrical impedance analysis (BIA) device sends a low-level electrical current through your body to measure resistance, which varies between fat, muscle, and water.
The InBody 570 provides:
- Body fat percentage
- Skeletal muscle mass
- Visceral fat level
- Segmental lean analysis (showing muscle distribution across your body)
- Basal metabolic rate
- Total body water
This data gives us actionable insights to design personalized training and nutrition plans.
For instance, if we notice a client has significantly less muscle mass in their left leg compared to their right, we might incorporate unilateral exercises to address this imbalance.
The real magic happens when we track changes over time.
Seeing muscle mass increase while body fat decreases provides concrete evidence that your training and nutrition plan is working, even when the scale doesn’t budge.
Losing Weight vs. Losing Body Fat
One of the biggest mindset shifts I encourage in clients is focusing on losing fat rather than losing weight.
The scale is a liar. It doesn’t tell you what you’re losing.
When someone says, “I need to lose weight,” what they usually mean is, “I need to lose fat.”
But rapid weight loss often means you’re losing muscle along with fat—or worse, losing mostly muscle and water with minimal fat loss.
This is one of the significant long-term health issues posed by the rise in popularity with weight loss drugs like Ozempic, Wegovy and Mounjaro.
We’ve seen this countless times: A client goes on a crash diet, loses 10 pounds quickly, but then plateaus, feels terrible, and eventually regains the weight.
Why?
Because they’ve damaged their metabolism by losing muscle mass, which reduces their basal metabolic rate.
Fat loss, by contrast, should be gradual and sustainable.
A healthy rate is 1-2 pounds per week, primarily from fat tissue while preserving or even building muscle.
Preservation of Muscle Tissue
Here’s where the rubber meets the road: muscle preservation is critical for long-term weight management and overall health.
Skeletal muscle is metabolically active tissue that burns calories even at rest.
The more muscle you have, the higher your resting metabolic rate.
When you lose muscle during aggressive dieting, you’re essentially downgrading your body’s engine from a V8 to a 4-cylinder.
Beyond metabolism, muscle tissue improves insulin sensitivity, supports joint health, enhances bone density, and improves overall functional capacity.
These benefits become increasingly important as we age.
The solution?
Strength training and adequate protein intake.
When losing weight, incorporating resistance training signals your body to preserve muscle while adequate protein provides the building blocks to maintain it.
This is especially crucial for busy professionals approaching middle age, as we naturally lose muscle mass (sarcopenia) starting around age 30.
Without intervention, you could be losing 3-5% of muscle mass per decade, slowly damaging your metabolism and health.
In the end, your weight is just a number.
Your body composition—specifically, how much of that weight is muscle versus fat—is what truly matters for both health and appearance.
So the next time your doctor fixates on BMI, ask for more comprehensive metrics like body fat percentage, visceral fat level, and metabolic health markers.
Your body is sophisticated and complex. The metrics we use to evaluate it should be too.
