Fat Distribution: Waist-to-Height and Waist-to-Hip Ratio
Central adiposity and cardiometabolic risk from waist, hip and height — with the paediatric caveats
Why use it
BMI says nothing about where fat sits, and two people at the same BMI can differ several-fold in visceral fat. Waist-to-height ratio in particular adds risk discrimination over BMI, needs only a tape measure, and uses one number as the cut-off across ages and both sexes.
About
Body fat carried centrally, around and inside the abdomen, is far more strongly associated with cardiometabolic disease than the same mass of fat carried on the hips and thighs. These two tape-measure indices describe that distribution. Waist-to-height ratio divides waist by height and is interpreted against a single boundary — keep the waist below half the height — that holds for men, women and children from about 5-6 years. Waist-to-hip ratio divides waist by hip and separates android from gynoid distribution, with sex-specific WHO thresholds, but it loses validity through puberty as the pelvis develops.
When to use
- Cardiometabolic risk assessment at any BMI, including in people of normal weight
- Screening children and adolescents from about 5-6 years, where it is among the better simple indicators
- Following an intervention, where waist often moves before weight does
- Assessing someone whose BMI is raised by muscle rather than fat
Formula
Pearls & pitfalls
- The single message "keep your waist to less than half your height" is as effective as any table and needs no calculation, which is why it is used in public health campaigns.
- Waist-to-height ratio holds its cut-off across ethnicities better than BMI does, and better than waist circumference alone, which needs population-specific thresholds.
- In children the 0.5 boundary is broadly stable from about 5-6 years through adolescence, which is unusual among anthropometric indices and makes it a practical screening tool without a growth chart.
- Waist can fall while weight is unchanged during resistance training; reporting both avoids the conclusion that nothing happened.
Next steps
A waist-to-height ratio at or above 0.5 should prompt blood pressure, fasting glucose or HbA1c, and a lipid panel, regardless of BMI. Measure the waist at the midpoint between the lowest rib and the iliac crest, at the end of a normal expiration, with the tape horizontal and not compressing the skin — technique, not the arithmetic, is where this measurement goes wrong.
Evidence
Ashwell and colleagues' meta-analysis (Obes Rev 2012) found waist-to-height ratio a better discriminator than BMI or waist circumference for diabetes, hypertension and cardiovascular outcomes, supporting the 0.5 boundary. The WHO expert consultation on waist circumference and waist-hip ratio (Geneva 2008) set the substantially-increased-risk thresholds at 0.90 for men and 0.85 for women and noted the limited value of waist-to-hip ratio in children.
References
- Ashwell M, Gunn P, Gibson S. Waist-to-height ratio is a better screening tool than waist circumference and BMI for adult cardiometabolic risk factors: systematic review and meta-analysis. Obes Rev. 2012;13(3):275-286. — link
- WHO. Waist Circumference and Waist-Hip Ratio: Report of a WHO Expert Consultation, Geneva, 8-11 December 2008. Geneva: WHO; 2011. — link
- Browning LM, Hsieh SD, Ashwell M. A systematic review of waist-to-height ratio as a screening tool: 0.5 could be a suitable global boundary value. Nutr Res Rev. 2010;23(2):247-269. — link
- NICE. Obesity: identification, assessment and management (CG189), updated 2022 — recommends waist-to-height ratio alongside BMI. — link