What is the difference between using Body Mass Index (BMI) and waist hip ratio for assessing health risks?

Waist-Hip Ratio vs BMI for Health Risk Assessment

For cardiovascular mortality risk prediction, waist-hip ratio (WHR) is superior to BMI, while for routine obesity screening and treatment decisions, combining BMI with waist circumference provides the most practical approach. 1, 2

Key Differences in Clinical Application

WHR Advantages for Mortality Prediction

• WHR carries the most important prognostic information for identifying adults at increased risk of cardiovascular and all-cause mortality, particularly in women, with those who died of cardiovascular disease having greater WHR at baseline compared to survivors 2
• Each 0.01 increase in WHR raises cardiovascular disease risk by approximately 5%, with the highest quintile conferring up to 66% increased risk of cardiovascular mortality 2, 3
• In patients with chronic kidney disease, WHR (but not waist circumference alone) was associated with cardiac events after adjusting for demographic factors, lifestyle characteristics, baseline CVD, and CVD risk factors 2
• WHR provides superior prediction across ethnically diverse populations because it adjusts for ethnic differences in body shape, whereas optimal BMI and waist circumference values differ substantially between Mexicans, Asians, blacks, and whites 2

BMI Limitations for Risk Assessment

• BMI does not account for body fat distribution, an independent risk factor for cardiovascular outcomes, and central adiposity captured by waist measurements may be missed when BMI is used as the only measure of obesity 1, 2
• BMI should be interpreted with caution in persons of Asian ancestry, older adults, and muscular adults 1
• In research studies, BMI was related to CVD mortality in age- and sex-adjusted models only, but not after full adjustment for other risk factors 3
• Among women with normal BMI, 19.0% had high waist circumference and 8.5% had high waist-hip ratio, demonstrating that BMI misses significant central obesity 4

Practical Clinical Algorithm

For Cardiovascular Risk Stratification

• Use WHR as the primary anthropometric assessment when predicting cardiovascular mortality risk, with increased risk occurring at WHR ≥0.95 for men and ≥0.80 for women 2
• Prioritize WHR measurement in patients with established chronic kidney disease for cardiac event prediction 2
• Apply WHR for uniform risk assessment across ethnically diverse populations 2

For Routine Obesity Screening and Treatment

• Use BMI to categorize patients initially, then add waist circumference for metabolic risk refinement in all patients with BMI <35 kg/m² 1
• Elevated waist circumference is defined as ≥40 inches (≥102 cm) in men and ≥35 inches (≥88 cm) in women, identifying individuals requiring weight reduction interventions 1
• For Asian populations, apply lower cut-points: ≥90 cm for men and ≥80 cm for women 1
• Combining waist circumference and BMI provides the best approach for assessing obesity-related risk in routine practice 1

Measurement Technique Considerations

WHR Measurement Complexity

• The American Heart Association does not recommend routine WHR use in general practice due to measurement complexity, despite its superiority for mortality prediction 1, 2
• WHR requires accurate measurement of both waist (at midpoint between lowest rib and iliac crest) and hip (at point of maximum circumference around buttocks), which is technically challenging and time-consuming 2

Waist Circumference Measurement

• Measure at the level of the iliac crest with patient standing in light clothing, tape positioned horizontally, snug but not compressing skin, at end of normal expiration 1
• Waist circumference thresholds are not reliable for patients with BMI >35 1

Disease-Specific Predictions

Type 2 Diabetes Risk

• WHR was strongly and independently related to incident type 2 diabetes in both men and women, with optimal cutoff values of 0.89 for men and 0.82 for women in Taiwanese population 2, 5
• Each anthropometric measurement (BMI, waist circumference, WHR) was equivalent in predicting type 2 diabetes in men, but in women, waist circumference and BMI showed the greatest risk ratio 2

Dyslipidemia Risk

• In non-Asian populations, WHR has a stronger association with dyslipidemia than BMI 2

Common Pitfalls to Avoid

• Do not rely on BMI alone in women, as measures of central adiposity (WHR, waist circumference) are better predictors of mortality in this population 6
• Do not use waist circumference thresholds for risk stratification in patients with BMI >35, as they are unreliable in this range 1
• Do not apply standard BMI or waist circumference cutpoints uniformly across ethnic groups without considering population-specific thresholds 1, 2
• Avoid using WHR in high-volume screening settings where measurement accuracy and reliability are concerns due to technical complexity 2