The Half-Height Waist String Test
Check your metabolic health risk in 30 seconds using only a piece of string
This low-cost metabolic screening tool applies the established clinical guideline that a healthy waist circumference should be less than half of your height. Unlike BMI, which misses fat distribution, this test specifically flags dangerous visceral belly fat—the kind associated with insulin resistance, fatty liver disease, and cardiovascular risk. All you need is a piece of string. The result is immediate and binary: pass or investigate further. Dr. Unwin uses it in general practice as a first-line conversation starter about metabolic health because it is accessible to anyone regardless of income or location.
- Where fat is stored matters far more than total body weight.
- Visceral belly fat is the primary driver of insulin resistance and metabolic disease.
- Free, immediate feedback drives behaviour change better than delayed, expensive testing.
- A simple binary result is more actionable than a complex index.
- Cut a string to exactly your standing heightMeasure and cut a piece of string, tape, or rope to precisely your height. This single length becomes your reference measure for the entire test.Pro tipA standard tape measure works equally well—note your height in centimetres or inches and simply divide by two to get the threshold number.
- Halve the string to create your waist thresholdCut or fold the string exactly in half. This half-length now represents the maximum healthy waist circumference for a person of your height.
- Wrap the string around your belly at its widest pointStand relaxed and wrap the half-length string around the widest part of your abdomen—typically at or just below the navel. Do not suck in your stomach or measure at the narrowest point.Pro tipBreathe normally and let your belly relax fully. Measurement at end of a normal exhale gives the most honest reading.WarningSucking in or measuring at the narrowest point gives a false pass and defeats the entire purpose of the test.
- Interpret the result and determine next stepsIf the string wraps comfortably around your belly, you pass. If it barely fits or does not reach, your waist-to-height ratio exceeds 0.5—a signal to investigate blood glucose, insulin levels, and liver function with a doctor.Pro tipEven a person who looks reasonably fit can fail this test if insulin resistance is routing fat storage to the abdomen specifically.WarningA passing result does not rule out all metabolic risk—this is a quick screen, not a comprehensive diagnosis.
Dr. Unwin cut a string to the height of podcast host Stephen Bartlett (6'1") and had him wrap the half-length around his belly on camera. Bartlett passed but only just, prompting a discussion about how insulin resistance specifically deposits fat abdominally and how even apparently fit, active people can be borderline on this measure.
Shared by Dr. David Unwin, UK GP and low-carb health advocate, on The Diary Of A CEO. The underlying guideline (waist less than half of height) is established in metabolic medicine literature.