Why BMI (Body Mass Index) Doesn’t Tell the Whole Story

You have probably heard of the term BMI (body mass index). It is based on your height and weight and is widely used to determine if you are in a healthy weight range. But it turns out that BMI alone may not be the best way to increase your shape.

Take a closer look at BMI

Calculated based on a person’s height and weight, BMI falls into four categories:

Underweight: BMI less than 18.5 Normal: BMI of 18.5 to 24.9 Overweight: BMI of 25 to 29.9 Obese: BMI of 30 or higher

But how useful is this number really?

“Probably for 90% or 95% of the population, BMI is fine as a general measure of obesity,” says Richard L. Atkinson, MD, a researcher and editor of the International Journal of Obesity.

But some critics take a different view. Scott Kahan, who leads the National Center for Weight and Wellness, says, “Traditionally, we define obesity by a certain limit on the BMI scale.” But judging whether someone is obese based on their size alone is old-fashioned and not very helpful, he says.

A football player who is very muscular may have a high BMI and yet his body fat is actually low. — Scott Kahan, MD

Kahan specializes in helping people manage excess weight that can lead to health problems, including diabetes and heart disease. At its center, measuring BMI is just a starting point. He sees people as overweight but healthy, and their BMI doesn’t really reflect their health risks.

“They’re heavy. Their BMI puts them in the obesity range. And yet their health is actually pretty good at every level we look at,” he says. “Their cholesterol and blood pressure are excellent. Their blood sugar levels are excellent. They don’t seem to have any health effects related to being overweight.”

While BMI is useful as a quick screening tool by a doctor or nurse, Kahan says, looking at that number alone isn’t enough.

A football player who is very muscular may have a high BMI and yet his body fat is actually low. — Scott Kahan, MD

Disadvantages of BMI

Your BMI reveals nothing about your body composition, such as how much muscle versus fat you have. Therefore, conclusions based solely on this number can be misleading, especially when it comes to the following:

How muscular you are: A few people have a high BMI, but not much body fat. Their muscle tissue pushes their weight up. An example: “A football player or a bodybuilder who is very muscular. Their BMI is quite high, yet their body fat is actually quite low,” says Kahan.

Your activity level: Someone who is very inactive may have a BMI in the normal range and have a lot of body fat, although they may not look out of shape.

“They have very low levels of muscle and bone – often older people, people in poor shape, sometimes people who are sick. Their BMI may be in the normal range, even though they have quite a lot of body fat compared to their lean body mass.” , says Khan. “Ultimately, they have similar risks to people who carry a lot of body fat and have a high BMI.”

Your Body Type: Are You Apple Shape or Pear Shape? The location of your fat makes a difference to your health. In general, it’s belly fat, or the “apple” shape, that has a higher health risk. When fat settles around the waist instead of the hips, the risk of heart disease and type 2 diabetes increases. Fat that builds up on the hips and thighs, or the “pear” shape, isn’t as potentially harmful.

Your age: The idea of ​​an ideal BMI can change with age. “People who are older should probably have a little more fat on them, [but] they shouldn’t have a BMI of 30,” Atkinson says.

He points out that people who are ‘a little overweight’ have a better chance of survival later in life than leaner people. The reasons for that aren’t entirely clear, but it may have to do with having reserves to draw on when fighting a disease. It’s hard to say for sure because many things affect your health.

Your ethnicity: There are many differences in BMI and health risk between ethnic groups. For example, Asian-Americans tend to develop health risks, including the risk of diabetes, at lower BMIs than whites. A healthy BMI for Asians ranges from 18.5 to 23.9, a full point lower than the standard range. And Asians are considered obese at a BMI of 27 or higher, compared to the standard BMI obesity measure of 30 or higher.

People of Indian descent are at higher health risks with relatively lower BMIs, Atkinson says. “The standard definition of being overweight is a BMI of 25 or higher. But if you’re from India, your risk of diabetes starts to rise with a BMI of about 21 or 22.”

In contrast, many African Americans may have a high BMI, but without the health risks that usually come with it. Compared to whites of the same weight and BMI, African-Americans tend to have less visceral fat (fat around their organs) and more muscle mass, Atkinson says. Therefore, an African-American with a BMI of 28, which is called overweight in the standard chart, can be just as healthy as a Caucasian with a BMI of 25.

Beyond BMI

So what other tools can you use besides BMI? You may want to grab your tape measure.

Waist size: For an accurate measurement, the tape measure should go around your waist, level with your hip bones in your lower back, and around your navel.

To prevent health problems from being overweight, men should keep their waist size no more than 40 centimeters. Women are not allowed to hold more than 35 inches. Again, there are some ethnic differences. According to the Joslin Diabetes Center, Asian men should keep their waistline to no more than 35.5 inches and Asian women to no more than 31.5 inches.

Waist-to-Height Ratio: This compares your waist circumference to your height. It may even be more helpful than just waist circumference, says Kahan. The goal is for your waist circumference to be less than half your height.

Other ways to measure body fat that may be more accurate than just using BMI include waist-to-hip circumference, skinfold thickness measurement, and ultrasound. Your doctor can help decide if these further tests may be needed.

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