The BMI Is Flawed

The BMI screening tool is flawed, and it is time to set the record straight.

As a medical weight loss doctor, it is my responsibility to discuss the health risks associated with being overweight. But doctors who have not received additional specialty training in obesity weight management have used it inaccurately. Before we address this issue, let’s briefly review what this metric is, and how to calculate your BMI.

What is BMI?

BMI stands for body mass index, and it is a screening tool that health professionals have been using for years to determine whether a person is the correct weight for their height. It is generally understood that individuals outside the BMI range may have higher health risks.

BMI measurements can be misleading.

Where’s the flaw?

BMI is calculated by taking your weight in kilograms divided by your height in meters squared. This results in your BMI score:

  • A BMI score of 18-25 is considered normal.
  • A score of 26-29 is labeled as being overweight.
  • A BMI of 30 or above is designated as obesity.

But here’s where it’s misleading: The BMI does not accurately measure body fat, nor does it take into account an individual’s muscle mass and overall body composition. Often, the consequences are irresponsible labels of obesity that can psychologically affect someone in a significant way. What’s worse is that the label is often given by a doctor.

So, someone may be registered as overweight even when they have a low percentage of body fat, and a normal-weight individual (according to the BMI) could be falsely labeled as healthy, despite having a high body fat percentage. We refer to these latter individuals as “skinny fat.” Those who are “skinny fat” may actually be at a much higher risk of health problems than those with a higher BMI, but a lower body fat percentage. I know, because I was one of them.

My own weight loss story

I generally did not have a weight problem until I gained 40 pounds during my first pregnancy. With a strong family history of diabetes, I struggled with both my blood sugars and controlling my weight. Thankfully, I had my own weight loss program to fall back on, and I was able to lose those 40 pounds.

But shortly thereafter, I tore my ACL and meniscus and went through 10 months of physical therapy to regain my normal gait again. That 10 months of inactivity, not-so-great eating, and turning 40 was enough to negatively affect my health. Most doctors out there would have told me, “Your BMI is normal. You don’t need to worry about your health.” But I knew the truth. My body fat percentage was abnormally high, so back on the journey, I went. I fought my way down to a normal body fat percentage and ignored even looking at my BMI.

The whole picture

Especially when it comes to weight loss, it is time to look at the right numbers. Body fat percentage, muscle mass, water weight, and overall body composition — the whole picture taken together — are a better indicator of health, which is why we have a specialized scale that determines those important metrics.

If you are ready to start your health journey and learn from my personal experiences, I invite you to schedule a free consultation with me at

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Dr. Angela Tran