Is There a Better Alternative to Measuring BMI?

While BMI is a popular method of calculating body fat, other measurements are better alternatives for determining weight level.

BMI is not an accurate indicator of overall health.

• People with more muscle mass and less body fat may weigh more, leading to higher BMI despite low-fat stores.
• BMI fails to distinguish between muscle, fat, and water and does not accurately indicate if weight reflects a healthy or unhealthy version of oneself.

Several alternatives for measuring body fat exist, each with its pros and cons. Some are beneficial in clinic and community settings, while others are used in large research studies to verify measurement techniques.

3 alternatives to measuring BMI

Other measurements commonly used in clinical and community settings include:

Waist circumference

This measures the amount of fat surrounding the abdomen (waist circumference).

Ways to measure waist circumference:

• Use a measuring tape.
• Place the measuring tape at the natural waist, between the lowest rib and top of the hip bone or at the navel button.
• Waist circumference over 35 inches in women (34 inches in Asian women) and 40 inches (36 inches in Asian men) indicates higher abdominal fat, associated with chronic diseases.

Benefits of measuring waist circumference:

• Easy and inexpensive.
• Abdominal fat is an ideal indicator of body fat.
• Studies have confirmed that waist circumference can predict disease development and health.

Downsides of this measurement:

• No standardization.
• No standard reference data for children.
• Less accuracy in individuals with a BMI of 35 or higher.
• Does not consider different body types and builds.

Waist-to-hip ratio (WHR)

WHR is a powerful indicator that measures abdominal obesity.

Ways to measure WHR:

• Measure waist circumference.
• Measure hip at widest diameter.
• Divide waist measurement by hip measurement.

WHR above 0.80 in women and 0.95 in men indicates higher fat storage in the abdomen, increasing the risk of heart and chronic diseases.

WHR lower than 0.80 in women and 0.95 in men suggests higher fat storage in the hip, indicating good health.

Benefits of measuring WHR:

• Easy and inexpensive.
• Better association with body fat.
• Studies have confirmed that WHR can predict disease development and health in adults.

Downsides of this measurement:

• May have measurement errors due to the need for waist and hip measurements.
• Measuring the hip is more complex than measuring the waist.
• Interpretation can be influenced by abdominal fat and lean muscle mass around the hips.
• Loss of information due to ratios.
• Less accuracy in individuals with a BMI of 35 or higher.
• Does not consider different body types and builds.

Skinfold thickness

This technique measures fat beneath the skin at various sites to estimate total body fat.

Steps involved in this measurement:

• Use a special caliper to measure skin fat.
• Pinch a fold of skin and use the caliper around it until a click sound is heard.
• Measure at different locations such as the trunk, thighs, front and back of the upper arm, under the shoulder blade, and back.

Benefits of measuring skinfold thickness:

• Fast, easy, convenient, safe, inexpensive, and portable (except for individuals with a BMI of 35 or higher).

Downsides of this measurement:

• Less precision and reproducibility compared to other methods.
• Difficult to measure in individuals with a BMI of 35 or higher.

Sophisticated methods used for measuring body fat

Sophisticated methods for measuring body fat include:

• Bioelectric impedance: It measures resistance to a small safe electric current through the body. Higher resistance indicates higher body fat.
• Air-displacement plethysmography: It uses the principle of underwater weighing but is done in the air. Individuals sit in a small chamber wearing bathing suits.
• Hydrometry: Individuals drink isotope-labeled water and provide body fluid samples, which are analyzed for body water, fat-free body mass, and body fat mass.

What is body mass index?

Body mass index (BMI) is a person’s weight in kilograms divided by the square of height in meters. It indicates the amount of body fat.

BMI is an inexpensive screening tool to measure body fat. Although it does not directly measure body fat, it can be correlated with more direct measures of body fat.

Categories of BMI:

• BMI value less than 18.5 kg/m2 is considered underweight.
• BMI values from 18.5 to 24.9 kg/m2 are healthy.
• BMI values from 25 to 30 kg/m2 are overweight.
• BMI higher than 40 kg/m2 is considered obese.

How do you calculate body mass index?

1. The default BMI on the tool is for a 5’5" person who weighs 100 lbs.
2. Use the switch on top to choose metric or imperial measurements.
3. Set the height and weight dials to match your own measurements.
4. View your BMI number at the center of the tool and see where you fall on the obesity chart.

BMI values are based on clinical data about averages across a wide range of people.

The BMI calculator allows you to screen yourself for obesity or extra weight. If your results are not in the healthy range, don’t worry too much. People with muscular builds may be classified as obese, even with a low body fat percentage and optimum health, because the BMI formula uses only two data points.

What are the limitations of using BMI?

There are several limitations associated with using BMI to assess body fat because it does not consider:

• How muscular you are.
• Your activity level and distribution of fat in your body.
• Your body type and risk of chronic diseases.
• Your age and survival.
• Your ethnicity and risk of diabetes.