New Research Says Waist to Height Ratio Is a Better Indicator of Health than BMI

It’s widely recognised that BMI (Body Mass Index) isn’t always the most accurate predictor of health, especially for individuals with athletic builds. However, despite its limitations, BMI still serves as a valuable initial assessment tool in clinical settings, especially when combined with other measurements. Nevertheless, emerging evidence suggests that there may be an even more informative metric to consider instead of relying solely on BMI.

By incorporating markers like waist-to-hip ratio or, in this case, waist-to-height ratio, healthcare professionals can efficiently assess their patients and gain a broader understanding of their health. A recent study published in Pediatric Research explores the potential superiority of waist-to-height ratio over BMI as a measure of health.

What Is BMI?

BMI (Body Mass Index) uses your height and weight to work out a measurement to gauge if your weight is healthy. The BMI calculation is:

Weight in kilograms divided by height in meters squared

A BMI of 18.5 – 24.9 is deemed as healthy.

According to research, BMI alone isn’t accurate in predicting metabolic health and may be particularly unreliable for athletes, the elderly and those who are pregnant.

Individuals who are lean, possess greater muscle mass, and have a lower body fat percentage may exhibit a higher BMI compared to those with a higher body fat percentage and less muscle mass. This discrepancy arises because muscle is denser than fat per pound. While individuals with lower body fat percentages and higher muscle mass are generally considered healthier, BMI might not accurately reflect this distinction.

Although BMI isn’t universally suitable and doesn’t consider muscle mass, in a clinical setting, it serves as an easy and time-saving method for doctors to assess a patient’s health initially. Is it entirely ineffective? No. However, is it beneficial for everyone, particularly those with a higher muscle-to-fat ratio? Probably not, at least when considered in isolation.

What is Waist-to-hip ratio?

BMI is frequently used in conjunction with waist-to-hip ratio for a more accurate measurement of health. The waist-to-hip ratio calculation is:

Circumference of the narrowest point of the waist divided by the widest point of the hips.

For men, a waist-to-hip ratio of less than one is deemed as healthy.

What Is Waist-to-height Ratio?

Waist-to-height ratio (WHtR), sometimes called waist-to-stature ratio (WSR), is also used as a marker of health. The WHtR calculation is

Waist circumference in centimetres divided by height in centimetres.

For men, a waist-to-height ratio below 0.5 or ‘waist less than half of height’ is deemed as healthy.

The Study

This extensive study aimed to compare two widely used methods for assessing body fat in children and adolescents: Body Mass Index (BMI) and waist circumference-to-height ratio (WHtR).

The research included 7,237 children, and researchers aimed to determine which method was more accurate in identifying excess body fat and distinguishing between fat and lean mass. They analysed data from the group of participants over several years, measuring their BMI, waist circumference and height, along with DEXA scans to directly measure total fat mass, trunk fat mass, and lean mass.

The Results

The results showed that WHtR was more effective than BMI in assessing body fat. WHtR was better at differentiating between fat and lean mass, providing a clearer picture of overall body composition. It remained stable across different ages and genders, making it a reliable tool for identifying excess body fat in children and teens.

The Conclusion

The study concluded that waist-to-height ratio is a simple and reliable method for assessing body fat in young people. Its ease of use and accuracy make it a valuable tool for healthcare professionals in identifying and addressing obesity in children and adolescents.

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What Does This Mean for Us?

This isn’t the only study that compares BMI and waist-to-height ratio. Another study, published by the Brazilian Archive of Digestive Surgery, found waist-to-height ratio to be superior to BMI in measuring cardiometabolic health.

NICE guidelines were recently reviewed and the new update encourages adults with a BMI below 35 kg/m² to measure their own waist-to-height ratio in conjunction with BMI. This could help indicate centrally stored adiposity (visceral fat around organs), which can be a helpful indicator of risk of illnesses.

If you suspect that your BMI results may be influenced by a higher degree of muscle mass, you can enhance accuracy by combining it with waist-to-height ratio. On the other hand, for those who have a higher body fat percentage, they could use the waist-to-height ratio in conjunction with BMI to make sure they are definitely within a healthy range or not.

The Research

• Waist-circumference-to-height-ratio had better longitudinal agreement with DEXA-measured fat mass than BMI in 7237 children: https://www.nature.com/articles/s41390-024-03112-8
• Factors affecting Body Mass Index, Advantages and its limitations: https://www.avten-edu.org.ng/journal/index.php/javten/article/view/306
• Waist-to-height ratio as an indicator of ‘early health risk’: simpler and more predictive than using a ‘matrix’ based on BMI and waist circumference: https://bmjopen.bmj.com/content/6/3/e010159
• Is the waist/height ratio a better parameter than BMI in determining the cardiometabolic risk profile of obese people?: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8735133/#:~:text=WHtR%20is%20a%20simple%20anthropometric,in%20kg%2Fm2%2036%20.
• NICE guidelines: https://www.nice.org.uk/guidance/CG189