Not Weight, Not BMI: Scientists Say This Body Ratio Is A Great Indicator Of Health

According to the National Center for Health Statistics (NCHS), obesity is a chronic health condition that affects 40.3% of adults in the United States. The 2024 report notes that "obesity is defined by body mass index (BMI)" because it's an inexpensive and simple screening tool to assess health and the risk of chronic illnesses. However, it acknowledges that BMI doesn't take into account actual body fat measurements and distribution. Instead, scientists say other measurements are more important for determining health, particularly waist-to-hip ratio (WHR).

BMI is calculated by simply dividing weight as kilograms by height as meters squared. Since muscle weighs more than fat, many athletes are considered obese simply based on this calculation despite having a low amount of body fat. WHR, on the other hand, is calculated by dividing waist circumference (usually at the smallest natural line) by hip circumference (usually the widest area). Because of that, it's a better indicator of fat levels and distribution in the body, especially around the abdomen.

For a study published in JAMA Network Open, researchers followed the health of more than 387,600 participants until their deaths. Then, they identified the individuals who developed health problems related to their weight — such as heart disease, high blood pressure, and type 2 diabetes — and cross-referenced those cases with their WHRs. The scientists found that WHR was more consistently and strongly associated with all-cause mortality than BMI and that BMI had no effect on WHR. They believe the most likely reason for these results is because WHR better reflects abdominal fat levels.

To understand why WHR reflects health and gauges chronic illness risk better than BMI, it helps to understand why body fat is associated with mortality. Visceral fat (abdominal fat) surrounds the liver and other internal organs. The problem is that it releases inflammatory compounds that contribute to a progression of chronic illnesses, such as insulin resistance and cardiovascular disease. On the other hand, hip and thigh fat is protective and associated with more ideal arterial calcification, blood pressure, blood sugar control, cholesterol, insulin, and insulin sensitivity.

Also, a study published in The BMJ found that bigger hip and thigh circumferences were linked to a lower risk of all-cause mortality. The researchers found that other measurements, including higher WHR, correlated with a higher mortality risk. Essentially, having more fat around the abdomen increases the risk of death from any cause. Another study published in Obesity Reviews found that having a large waistline is more strongly related to cardiovascular-related illnesses than overall obesity, and it's even associated with asthma, dementia, and some cancers.

All of these studies indicate that WHR provides a more well-rounded estimate of disease risk than weight alone. According to the World Health Organization, a healthy WHR is below 0.9 for males and below 0.85 for females. You may not have control over how your body distributes and stores fat, but a study published in PLOS One found that eating little to no processed foods (some of the unhealthiest foods for your heart) may reduce WHR. Those who struggle to lose belly fat, though, may achieve better results with GLP-1s, which are considered some of the best peptides to improve your body.