Body mass index (BMI) is categorized into several ranges to indicate weight status. A BMI under $${}18.5$$ is considered underweight. A BMI between $${}18.5$$ and $${}24.9$$ falls within the normal or healthy weight range. An adult with a BMI between $${}25$$ and $${}29.9$$ is classified as overweight, while a BMI of $${}30$$ or higher indicates obesity.

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Body mass index (BMI) is a measure utilized by medical doctors to determine if an individual is obese. It uses the formula of weight (kg) divided by height (m^2) squared.

Body Mass Index (BMI)

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

Despite BMI being used widely by medical doctors, BMI is outdated and lacks inclusivity due to different limitations:
- Lack of diversity
- Oversimplification
- Metabolic health is ignored
- Negative consequences of BMI usage

Limitations of Body Mass Index (BMI) as a Health Metric 

A Body Mass Index (BMI) chart is a visual tool that illustrates weight status categories by plotting an individual's weight against their height. The chart typically uses a horizontal axis for weight (in both pounds and kilograms) and a vertical axis for height (in both feet/inches and meters). The area of the chart is divided into distinct, often colored, regions that correspond to the primary BMI classifications: underweight, normal range, overweight, and obese.

BMI Chart

An individual is classified as underweight if their Body Mass Index (BMI) is less than 18.5. For example, on a standard BMI chart, this category can range from a person who is 4'11" and weighs 90 pounds to someone who is 6'6" and weighs up to approximately 160 pounds.

Underweight (BMI < 18.5)

The normal or healthy weight range is defined by a Body Mass Index (BMI) between 18.5 and 25. As an illustration from a BMI chart, this range could include a person at 4'11" weighing between 90 and 120 pounds, or a person at 6'6" weighing between 160 and 220 pounds.

Normal Weight Range (BMI 18.5-25)

An adult is considered overweight if their Body Mass Index (BMI) is between 25 and 30. For instance, on a standard BMI chart, this category can apply to a person who is 4'11" and weighs between 120-140 pounds, or a person who is 6'6" and weighs between 220-265 pounds.

Overweight (BMI 25-30)

An adult is classified as obese if their Body Mass Index (BMI) is 30 or higher. As an example from a BMI chart, this category could include an individual at 4'11" weighing between 140 and 350 pounds, or an individual at 6'6" weighing between 265 and 350 pounds.

Obese (BMI > 30)

An individual is 1.75 meters tall and weighs 70 kilograms. Using the standard formula where the final value is calculated as weight in kilograms divided by the square of the height in meters, what is this individual's Body Mass Index (BMI), rounded to one decimal place?

According to the Centers for Disease Control and Prevention (CDC), Body Mass Index (BMI) classifies adult weight into specific categories. A BMI between 25 and 29.9 indicates an individual is overweight, a BMI of 30 or higher is classified as obese, and a BMI over 40 indicates severe obesity, which carries a risk of death.

BMI Weight Classifications

Body mass index (BMI) is less effective for assessing individual health because it relies solely on height and weight, failing to account for factors like fitness level and body composition. For example, an athlete may have a high BMI due to muscle mass rather than fat. Additionally, BMI scales do not account for variations in body composition across different racial and ethnic groups, leading the American Medical Association to recommend in $${}2023$$ that it be removed as a standard measure of health.

Limitations of Body Mass Index (BMI)

Body Mass Index (BMI) Ranges

An individual is classified as underweight when their Body Mass Index (BMI) is below $${}18.5$$.

Underweight Classification by BMI

An individual is considered to be within a normal weight range when their Body Mass Index (BMI) is between $${}18.5$$ and $${}25$$.

Normal Weight Classification by BMI

An adult is classified as overweight when their Body Mass Index (BMI) falls between $${}25$$ and $${}29.9$$. This indicates that the individual weighs more than what is generally accepted as healthy for their height.

Overweight Classification by BMI

Obesity is a condition defined by having a Body Mass Index (BMI) of $${}30$$ or higher. This classification indicates a weight level that exceeds generally accepted healthy limits for a person's height.

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