BMI Explained: What It Is and Why It Matters

You just saw your BMI—now what?

• Is this number good or bad?

• Can I be healthy and still be in the “overweight” category?

• Why does my doctor care so much about this?

• Should I care at all?

If you’re confused, you’re in good company. Between medical jargon, internet opinions, and outdated charts, understanding your Body Mass Index can feel more frustrating than helpful.

At OnPoint Nutrition, we’ve guided over 65,000 individuals through this exact moment—helping them decode numbers like BMI and understand how they fit into a real, personalized approach to health.

By the end of this article, you’ll have a clear sense of what BMI is, how it’s calculated, what it can tell you about your health—and what it can’t. Let’s unpack it together.

What is BMI?

Body Mass Index (BMI) is a quick calculation based on your height and weight, often used to estimate whether your weight falls within a range that may raise health concerns. While it’s a widely used screening tool, it’s just one piece of the puzzle—and it doesn’t tell the whole story about your health.

BMI is designed to be a quick screening tool to estimate whether a person falls into categories like underweight, normal weight, overweight, or obese—categories that can help flag potential health risks. However, it has important limitations. BMI doesn’t distinguish between muscle and fat, which means it may misclassify individuals with higher muscle mass, such as athletes or those with more muscular builds.

Here is the standard chart

How is BMI Calculated?

BMI is calculated using a simple formula that compares your weight to your height: your weight in kilograms divided by your height in meters squared (kg/m²). For those using pounds and inches, most online BMI calculators will convert the measurements for you. 

Here’s how you can calculate it:

• Formula: BMI = weight (kg) / height (m²)
• Example: If you weigh 70 kg and are 1.75 meters tall, your BMI is 22.86 (70 / 1.75²).

While the formula itself is straightforward, interpreting the result in a meaningful way often requires a closer look at your overall health, lifestyle, and body composition.

Why Does BMI Matter?

Understanding your BMI can offer a meaningful starting point in evaluating your overall health. While it’s not a diagnostic tool, a high BMI is often correlated with an increased risk of chronic conditions like heart disease, type 2 diabetes, and certain cancers. Used thoughtfully, BMI can help flag potential concerns early—opening the door for proactive lifestyle shifts and personalized care. It’s not the full picture, but it’s a signal worth paying attention to on your journey toward better health.

The Limitations of BMI

While BMI can be a helpful screening tool, it’s far from a perfect measure of health—and it’s important to understand where it falls short.

Here’s what BMI doesn’t tell you:

• Muscle vs. Fat: BMI doesn’t differentiate between lean muscle and body fat. This means individuals with high muscle mass—like athletes—may be labeled as overweight or obese, even if their body fat percentage is low.
• Age and Gender Differences: As we age, our body composition naturally shifts, and women and men store fat differently. BMI doesn’t account for these variations, which can lead to misleading classifications.
• Ethnicity Considerations: Research shows that the health risks associated with BMI can vary across ethnic groups, making one-size-fits-all thresholds less accurate for some populations.

In short, BMI is best used as a starting point, not a diagnosis. Understanding its limitations ensures you use it in context—alongside more personalized and nuanced assessments of your health.

Alternatives to BMI

Because BMI has its limitations, it’s often most useful when combined with other assessments that provide a fuller picture of your health.

Additional tools that can offer deeper insight include:

• Waist Circumference: This simple measurement captures abdominal fat, which is strongly linked to increased risk for heart disease, type 2 diabetes, and other chronic conditions.
• Body Fat Percentage: Unlike BMI, this metric distinguishes between fat and lean mass, offering a more accurate view of your body composition and overall health.
• Waist-to-Hip Ratio: This ratio helps assess fat distribution—particularly around the midsection—which can be a more telling indicator of metabolic health than BMI alone.

When it comes to health, no single number tells the whole story. A more comprehensive approach—guided by qualified professionals—can help you see the full picture and take informed steps toward long-term wellness.

Your BMI Doesn’t Tell the Whole Story—But Your Nutrition Might

BMI can offer a quick glimpse at your health, but it doesn’t reveal what’s actually going on inside your body. It doesn’t tell you how much of your weight is muscle vs. fat. It doesn’t account for where you carry weight, how you eat, or how your body is functioning day-to-day.

That’s where nutrition comes in.

At OnPoint Nutrition, we use BMI as just one piece of the puzzle. Our registered dietitians dig deeper—helping you understand your body composition, metabolic health, and how your eating patterns are supporting (or stalling) your goals. Whether your BMI is high, low, or right in the middle, your nutrition plays a defining role in your health outcomes.

Wondering what your BMI means—and what to do about it?

Whether your BMI is high, low, or right in the middle, your nutrition plays a powerful role in how you feel, function, and live.

Your body is unique. Your plan should be too.Let’s stop guessing and start making progress—on your terms, with expert support that actually fits your life.