Waist-to-height ratio: where the 0.5 and 0.6 cut-offs come from, and what they do not tell you

"Keep your waist to less than half your height" is the public-health sentence in a 2010 review of waist-to-height ratio, and it is the sentence NICE asks clinicians to explain. It is also a boundary value that someone derived from data, on particular people, measured in particular ways. This article looks at where the 0.5 cut-off and the higher 0.6 boundary come from, what the studies behind them actually measured, and the situations in which the same number means less than it seems. For the basics of the ratio itself, see Waist-to-height ratio: a two-minute marker of where your fat sits.

Where 0.5 comes from

The 0.5 boundary is not a physiological threshold at which something in the body switches on. It is a mean of screening cut-offs. In a 2010 systematic review, Browning, Hsieh and Ashwell collated 78 studies, published in English between 1950 and 2008, exploring waist-to-height ratio (WHtR) and waist circumference or BMI as predictors of diabetes and cardiovascular disease. Receiver operating characteristic (ROC) analysis gave mean boundary values for WHtR, covering all cardiometabolic outcomes, from studies in fourteen countries and including Caucasian, Asian and Central American groups, of 0.50 for men and 0.50 for women (PMID 20819243). The review also included cross-sectional analyses in children, and the abstract does not restrict that mean of 0.50 to adults.

That is why 0.5 is best read as a screening boundary — a line drawn to separate people with the recorded outcomes from people without them — not as the point above which harm begins.

How strong the evidence behind it is

The strongest summary is a 2012 meta-analysis by Ashwell, Gunn and Gibson. Thirty-one papers met the inclusion criteria. They used ROC curves to compare how well body measures distinguished adults with and without hypertension, type 2 diabetes, dyslipidaemia, metabolic syndrome and cardiovascular outcomes. Together the studies involved more than 300,000 adults in several ethnic groups. WHtR had significantly greater discriminatory power than BMI. Compared with BMI, waist circumference improved discrimination of adverse outcomes by 3%, and WHtR improved it by 4–5%. Within studies, WHtR was significantly better than waist circumference for diabetes, hypertension, cardiovascular disease and all outcomes, in men and in women (PMID 22106927).

Two points about what this does and does not show:

• These are screening studies. They measure how well a number sorts people who already have the outcomes from people who do not. They do not show that lowering the ratio changes outcomes.

• Whether most of the 31 papers were cross-sectional is not stated in the 2012 abstract. The 2010 review counted 22 prospective analyses and cross-sectional analyses (44 in adults, 13 in children). An association between a higher ratio and more disease is not evidence that the ratio, rather than what it stands for, causes anything, and neither review is a trial of lowering it.

Mortality data point the same way, and they come from two different British sources. A Cox model was applied to the prospective Health and Lifestyle Survey and the cross-sectional Health Survey for England. In British adults, WHtR was a better predictor of mortality risk than BMI, and years of life lost were estimated for different values of the ratio, for both sexes, at ages 30, 50 and 70 (PMID 25198730). This describes an association in that model. It is not an effect of changing one's waist.

What 0.5 adds to BMI

The practical argument for the ratio is that it catches people BMI misses. In adults from the UK National Diet and Nutrition Survey 2008–2012 (1,453 adults), 35% of those classed as "no increased risk" by a combined BMI and waist-circumference matrix had a WHtR of 0.5 or above. Among adults with a "healthy" BMI, those at or above 0.5 had some significantly higher cardiometabolic risk factors than those below it, after adjustment for age, sex and BMI (PMID 26975935). That is a cross-sectional comparison in one national sample, and it describes risk factors, not later events.

Where 0.6 comes from

UK NICE guideline NG246 on overweight and obesity management (published in 2025; the adult classification below is a 2022 recommendation carried into that guideline) uses WHtR in adults with a BMI under 35 kg/m². The bands are 0.4 to 0.49 (healthy central adiposity, described as no increased health risk), 0.5 to 0.59 (increased central adiposity, increased health risk) and 0.6 or more (high central adiposity, further increased health risk). NICE states that these bands can be used for people with a BMI under 35 of both sexes and all ethnicities, including adults with high muscle mass. In the rationale, the cut-off from individual studies was generally around 0.5, in line with the wider evidence; the committee noted that 0.6 or more indicates a further increase in risk. The guideline uses the measurements to help assess and predict health risks (for example type 2 diabetes, hypertension or cardiovascular disease). Adults whose measurement indicates an increased health risk are pointed toward further clinical assessment, such as a cardiometabolic risk-factor assessment. The bands are not a diagnosis. The guideline does not cover pregnancy.

The 2025 Lancet Diabetes & Endocrinology Commission on the definition and diagnostic criteria of clinical obesity takes a different question: when excess adiposity is present, and when it is a clinical illness. It recommends confirming excess adiposity by direct measurement of body fat, where available, or by at least one anthropometric criterion — waist circumference, waist-to-hip ratio or waist-to-height ratio — in addition to BMI, using validated methods and cut-offs appropriate to age, sex and ethnicity. It separates that confirmation from the diagnosis of clinical obesity, which requires evidence of reduced organ or tissue function due to excess adiposity, or substantial age-adjusted limitation of daily activities reflecting the effect of that excess, or both (PMID 39824205). An erratum to the Commission corrected the list of endorsing organisations and translations, not these criteria.

Where the number means less than it seems

Measurement site changes the value. There is no single agreed place to put the tape. In 542 predominantly white adults aged 20–67 (223 men and 319 women), waist circumference differed across four common sites in women, except for the iliac crest versus the midpoint, while in men the differences were not significant. Using cut-offs of more than 88 cm in women and more than 102 cm in men, the site alone moved the apparent share with abdominal obesity from 31% to 55% in women and from 23% to 34% in men (PMID 19343017). A systematic review of 120 studies (236 samples) found that the protocol did not substantially influence the association of waist circumference with all-cause and cardiovascular mortality, cardiovascular disease and diabetes (PMID 17956544). Those are different findings: the site can move a person across a cut-off, while the choice of protocol did not substantially change the association with those outcomes. Two readings are comparable when they were taken the same way.

Children and adolescents. A 2016 meta-analysis of 34 paediatric studies that reported ROC areas found that WHtR did not have significantly better screening power than BMI or waist circumference for most cardiometabolic outcomes. The exceptions in that analysis were elevated triglycerides compared with BMI, and a high metabolic risk score compared with waist circumference (PMID 27452904). NICE NG246, in a recommendation amended in January 2026, also sets the same three bands for children and young people aged 5 years and over, of both sexes and all ethnicities: 0.4 to 0.49, 0.5 to 0.59, and 0.6 or more. As in adults, that is a classification used to predict health risks, not a diagnosis. A ratio near 0.5 in a child is a reason to look further, not a result that stands on its own.

Pregnancy and high muscle mass. NG246 does not cover pregnancy, so its bands are not a pregnancy recommendation. For adults with high muscle mass and a BMI under 35, NICE applies the same bands; its caution for that group is about BMI, which may be a less accurate measure of central adiposity there.

Near the line. Because 0.5 is a point chosen on a continuous measurement, 0.49 and 0.51 are adjacent readings. The trend across repeated, identically taken measurements says more than one reading.

What to do with the number

A WHtR at or above 0.5 is a reason to look at the rest of the picture with a doctor, rather than a verdict. NICE points adults with a BMI under 35 whose ratio indicates increased risk toward further clinical assessment, such as cardiometabolic risk factors. The risk factors compared in the National Diet and Nutrition Survey analysis included triglycerides, total and HDL cholesterol, HbA1c, fasting glucose and blood pressure. For how glucose markers are read, see When fasting glucose and HbA1c disagree; for measuring what the ratio stands in for, see Body composition instead of weight.

What the evidence does not say

• It does not show that 0.5 is a biological threshold: it is a mean of screening boundaries.

• It does not show that bringing the ratio below 0.5 changes cardiovascular events or lifespan; the mortality figures are estimates from an observational model.

• It does not make WHtR a diagnosis: the guideline uses it to help assess and predict health risks, and to flag people for further assessment.

• It does not show that 0.6 was derived as a second ROC mean in the same way as 0.5. In the NICE rationale, study cut-offs were generally around 0.5, and 0.6 or more is noted as a further increase in risk.

This material is for information only and does not replace a consultation with a doctor.

Sources

• Browning LM, Hsieh SD, Ashwell M. A systematic review of waist-to-height ratio as a screening tool for the prediction of cardiovascular disease and diabetes: 0·5 could be a suitable global boundary value. Nutr Res Rev. 2010. PMID 20819243.

• 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. PMID 22106927.

• Ashwell M, Mayhew L, Richardson J, Rickayzen B. Waist-to-height ratio is more predictive of years of life lost than body mass index. PLoS One. 2014. PMID 25198730.

• Ashwell M, Gibson S. 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. BMJ Open. 2016. PMID 26975935.

• Mason C, Katzmarzyk PT. Variability in waist circumference measurements according to anatomic measurement site. Obesity. 2009. PMID 19343017.

• Ross R, et al. Does the relationship between waist circumference, morbidity and mortality depend on measurement protocol for waist circumference? Obes Rev. 2008. PMID 17956544.

• Lo K, Wong M, Khalechelvam P, Tam W. Waist-to-height ratio, body mass index and waist circumference for screening paediatric cardio-metabolic risk factors: a meta-analysis. Obes Rev. 2016. PMID 27452904.

• Rubino F, et al. Definition and diagnostic criteria of clinical obesity. Lancet Diabetes Endocrinol. 2025. PMID 39824205.

• National Institute for Health and Care Excellence. Overweight and obesity management (NG246). Published 14 January 2025; adult waist-to-height classification is the 2022 recommendation carried in that guideline. Child bands: recommendation amended January 2026, ages 5 years and over.