It may be tempting to think that BMI is the alpha and omega of body-fat measurements. Not by a long shot. Another useful anthropometric parameter is waist-to-hip ratio (WHR).
WHR reflects the proportion of fat located around the waist and hips. Those with more weight at the level of the waist have a higher risk of heart disease and diabetes compared with those with more weight at the hips. WHR is calculated by dividing waist circumference by hip circumference. An ideal value for women is 0.8 or less and that for men is 0.95 or less.
WHR has been gaining traction in recent years. For instance, the University of Alabama cites research demonstrating that WHR was a better predictor of mortality in those aged 75 years or more than BMI.
Here’s a closer look at how WHR can be a strong predictor of health, based on recent research.
Sleep apnea
Overnight oximetry is a cost-effective test for diagnosing obstructive sleep apnea. It is unclear, however, whether BMI or WHR is a better predictor of abnormal ambulatory overnight oximetry results.
In a retrospective cross-sectional study published in Frontiers in Cardiovascular Medicine, Mayo Clinic investigators reviewed data from 393 men who received ambulatory overnight oximetry as ordered by their preventive medicine physicians. Of these patients, 295 exhibited abnormal results.
On analysis, WHR was the best predictor of abnormal oximetry results followed by BMI ≥30.0 kg/m2, age ≥55 years, and snoring. Of note, WHR was strongly associated with abnormal oximetry results in obese and non-obese participants. Overall, 88 men with abnormal oximetry results received polysomnography, with 91% diagnosed with obstructive sleep apnea.
“While our findings need to be confirmed in a prospective study using serial polysomnographic assessments, middle-aged men who snore and have a WHR ≥1.0 should perhaps be directly referred to a sleep clinic or receive cardiorespiratory polygraphy for further evaluation,” concluded the authors. “Our study adds to the understanding of central adiposity as it relates to sleep disordered breathing, and how a technically simple measurement, such as the WHR, may assist in screening for, and diagnosing, (obstructive sleep apnea).”
Heart attack
Results from a systematic review and meta-analysis published in Medicine indicated that WHR may be of cardinal importance in predicting the burden of heart disease in young and middle-aged adults. Specifically, the researchers found that WHR more strongly predicted risk in women compared with men.
The authors hypothesized that central obesity, which is measured by WHR, contributes to MI via oxidative stress, inflammation, steroid hormones, and alteration in hormone levels. They cited research from the Framingham Heart Study and Jackson Heart Study that have demonstrated that visceral fat hyperplasia can lead to oversaturation and spill of fat into lean tissues, such as the heart and liver, thus mediating heart and metabolic disease.
The authors also noted that adipose tissue fat cells can facilitate atherosclerotic processes, and excessive visceral fat plays a part in insulin resistance, hypertriglyceridemia, and other proatherogenic factors. These processes can trigger endothelial vasomotor dysfunction, hypercoagulability, and dyslipidemia, thus yielding MI
“In light of these results, first, the ability of WHR to predict MI risk is evident, and healthcare professionals should consider the pivotal role of WHR in identifying populations at higher risk of MI, especially in women,” wrote the authors.
The authors also recommended that WHR could be included in health education so patients understand that normal body weight does not mean lack of abdominal obesity. The authors also cautioned that rehabilitation professionals not only focus on BMI but also consider WHR and stressed that “as a central obesity index, WHR is more clinically relevant than BMI and merits increased attention, especially in terms of the acute onset of disease, to reduce the risk of morbidity.”
Bottom line
Although BMI is useful, as a marker of central obesity, WHR could be more important. Given the ease of calculating WHR and its clinical utility, this measure should be considered by healthcare professionals when evaluating health.