Waist Circumference and Waist-to-Hip Ratio
Carrying too much body fat is generally termed obesity. The worldwide prevalence of obesity has tripled since 1975, with 13% of the global population considered obese in 2016. Obesity is associated with a lot of poor health outcomes including but not limited to, cardiovascular disease, type 2 diabetes, musculoskeletal impairments, and certain cancers.
Obesity is generally caused by a positive energy balance, or energy intake (from habitual diet) exceeding energy expenditure (e.g. physical activity). Excess calories from fat, carbohydrate, and protein in the diet that have not been metabolised are then stored as fat throughout the body. As more excess energy is consumed, fat stores expand, increasing the potential for obesity.
An individual is defined as obese when their body mass index [weight expressed relative to height (BMI)] is ≥30kg/m2. However, BMI fails to consider muscle mass, meaning an individual with an obese BMI, may in fact have a low body fat percentage. Conversely, an individual with a non-obese BMI may have a high body-fat percentage.
Gold standard methods of measuring body fat percentage (e.g. underwater weighting, bodpod, DEXA scans) are generally inaccessible to most people and somewhat expensive. As such, measuring the circumference of certain anatomical sites (e.g. waist and hip) is an inexpensive, easy, and reliable method of assessing the level and distribution of body fat for the majority of individuals.
Waist and Hip Measurements
Men typically store excess body fat in the waist and abdomen (android region) which is why the classic overweight male ‘apple shape’ is described as an android shape. Women however, will typically store body fat in the hips and gluteal area (gynoid region) creating a pear-like or gynoid shape.
The android and gynoid regions are important considerations because a person can have a ‘normal’ BMI and still have a lot of abdominal fat. On the other hand, a person can be classified as ‘obese’ according to their BMI but have very little abdominal fat.
The waist circumference is a good indicator of overall body fatness in its own right because there is a strong relationship between abdominal body fat and that stored elsewhere in the body. However, central fat storage (also referred to as android, visceral, or abdominal adiposity), which is the type of fat that specifically builds up around the middle of the body, is considered more harmful because:
- more fat is being stored around the major organs (heart, liver, pancreas)
- more fat is being stored inside skeletal muscle
- fat deposits around the major organs and skeletal muscle causes inflammation
A waist circumference measurement directly measures central fat storage and provides a quick and reliable indication of risk. The waist to hip ratio however considers central fat storage relative to body fat stores in the hips, to also predict the risk of poor health outcomes in the future and disease.
There are many health-related consequences of central fat storage including:
- high blood pressure
- raised cholesterol
- elevated blood sugar levels (including insulin resistance)
- poorer outcomes in response to COVID-19 infection
If more fat is stored around the hips compared to the abdomen (pear-shaped) there is less central fat storage, and thus a lower risk of poor health outcomes. Alternatively, if more fat is stored around the abdomen compared to the hips (apple-shaped), then the risks of disease and other poor health outcomes is increased.
Factors Affecting Hip and Waist Measurements
- Age: As people get older they gradually lose muscle mass as a result of a process called sarcopenia. Fat gradually replaces lost muscle mass and contributes to greater hip or waist circumferences.
- Hormonal Fluctuations: Changes in circulating hormone levels (e.g., oestrogen, testosterone) are linked with the re-distribution of stored body fat.
- Diet: Besides consuming more energy than is burnt (positive energy balance), certain dietary patterns are specifically linked with central fat storage, including:
- Consuming a lot of sugar-sweetened beverages (soda, fruit juices, etc)
- Having a low fibre intake (not consuming sufficient fruits, vegetables, and whole grains)
- Having a low protein intake (lean meats, fish, eggs, etc)
- Having a high meal frequency (snacking)
- Having a high intake of foods high in trans fatty acids (crisps, pastries chocolate, and ice-cream)
- Alcohol: Consuming more than the recommended amount of alcohol is linked with a greater waist circumference, particularly in men.
- Exercise: Engaging in moderate to vigorous physical activity contributes to daily energy expenditure as well as burning central fat stores. There is some limited evidence that core stability training can aid with reducing waist circumference also.
- Sedentary Behaviour: Remaining in a seated position (desk work, driving, watching television) for large amounts of time per day is linked to a greater waist circumference.
- Stress: Some evidence suggests that the release of the fight or flight hormone, cortisol, which is triggered in stressful situations, is linked with central body fat storage.
- Genetics: Early evidence suggests people with certain genotypes are at higher risk for storing fat in central areas. Genes that control proteins like leptin and cortisol seem particularly important.
- Sleep: Not getting enough sleep, or even lower quality sleep, is linked with a greater waist circumference, especially for certain sleep conditions (e.g. sleep apnoea).
Other Factors Affecting Waist and Hip Measurements
Tape misplacement: If you are measuring your own waist circumference or waist to hip ratio, placing the tape in the same place for each assessment is essential. If the tape is in a slightly different spot each time this could affect the recorded value. Anatomical landmarks like the rib, pelvic, hip bones, navel (belly button), and skin tags, moles, freckles, or skin lesions can also help you to be more consistent with your measurement position over time.
Proximity to meals: You should also consider how close to your meals you are taking your waist measurement. After a meal, stomach distension (bloating) naturally takes place as a signal of fullness. Bloating can push fat stores closer to the surface of the skin, increasing waist circumference. If you take a waist measurement too close to a meal, this can be falsely interpreted as an increase in central fat storage.
Clothing: You should also consider what clothes you have on during both waist and hip assessment. Clothing factors to be particularly aware of are the tightness of a belt (if one is worn), the thickness of clothing (e.g., a jumper vs. a t-shirt), as well as whether or not there is anything in your pockets.
Measuring Waist and Hip Circumferences
- Locate the bottom of the ribs (bottom/smallest rib) and the top of the hips (pelvic bones)
- Place the tape measure halfway between these two points, around the midline of your body (normally just above the belly button)
- Ensure the tape is pulled tight but isn’t digging into the skin
- Breathe out naturally and record the measurement (to the nearest 0.1 cm)
- For best practice repeat this process twice, and record the average score
- Place the tape measure around the hips at the point where the width is greatest (above the gluteal fold)
- Record the measurement (to the nearest 0.1 cm)
- For best practice repeat this process twice, and record the average score
Calculating Waist to Hip Ratio:
To calculate waist to hip ratio, simply divide waist circumference measurement by hip circumference measurement. Waist-to-hip ratio is normally expressed to two decimal places. For example:
Waist = 94 cm
Hip = 98 cm
94÷98 = 0.95
Note: Refer to classification for interpretation.
Classification of Waist Hip Ratio
To interpret the results of the above waist to hip ratio calculation, compare the results obtained to the following table.
|Low Risk||High Risk|
|Male||<0.90cm (0.35 inches)||≥0.90cm (0.35 inches)|
|Female||<0.85cm (0.33 inches)||≥0.85cm (0.33 inches)|
Alternatively, use the following waist to hip ratio calculator.
It is important to acknowledge that waist to hip ratio is less informative regarding future health risk compared to waist circumference alone, simply because the link with overall body fat content is not as strong as it is for waist circumference. However, both do still hold merit in assessing health risk.
Classification of Waist Measurements
Given the risks associated with an increased waist circumference, specific reference and classification data also exist for men and women based on waist measurements alone. This data also considers ethnicity, which is known to also influence a person’s risk of some diseases and conditions.
Furthermore, for individuals from certain ethnic minority backgrounds, there appears to be a greater risk of metabolic dysfunction at lower levels of central fat storage, compared to individuals from other ethnic backgrounds. This is why there is adjusted reference data for these populations.
|Low Risk||High Risk||Very High Risk|
|White European, Black African, Middle Eastern, and Mixed Origin|
|Male||<94cm (37 inches)||94-102cm (37-40 inches)||>102cm (40 inches)|
|Female||<80cm (31.5 inches)||80-88cm (31.5-34.6 inches)||>88cm (34.6 inches)|
|African Carribean, South Asian, Chinese, and Japanese Origin|
|Male||<90cm (35.4 inches)||>90cm (35.4 inches)|
|Female||<80cm (31.5 inches)||>80cm (31.5 inches)|
A Note for Exercise Professionals:
Waist circumference and waist to hip ratio should be routinely used by exercise professionals (e.g. personal trainers) as a means of screening and monitoring clients. In cases where clients are identified as high risk, a referral to a suitably trained medical professional should be made before any exercise prescription or training is performed.