The waist is the part of the

abdomen The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

between the

rib cage The rib cage or thoracic cage is an endoskeletal enclosure in the thorax of most vertebrates that comprises the ribs, vertebral column and sternum, which protect the vital organs of the thoracic cavity, such as the heart, lungs and great ve ...

and

hips In vertebrate anatomy, the hip, or coxaLatin ''coxa'' was used by Celsus in the sense "hip", but by Pliny the Elder in the sense "hip bone" (Diab, p 77) (: ''coxae'') in medical terminology, refers to either an anatomical region or a joint ...

. Normally, it is the narrowest part of the

torso The torso or trunk is an anatomical terminology, anatomical term for the central part, or the core (anatomy), core, of the body (biology), body of many animals (including human beings), from which the head, neck, limb (anatomy), limbs, tail an ...

. ''Waistline'' refers to the horizontal line where the waist is narrowest, or to the general appearance of the waist.

Structure

Because of this and because the waist is often synonymous with the stomach, one can become confused as to the exact location of the waist. Another confusing factor is that the waistline differs on different people. A study showed that self-reported measurements, as opposed to measurement done by a technician, underestimated waist circumference and this underestimation increased with increased body size. In the study, waist circumference measured at the level of the umbilicus was larger than that measured at the natural waist. To locate the natural waistline, one need simply stand upright and then tilt over to the side, keeping the legs and hips straight. Where the torso creases is the natural waistline.

Size

Waist measurement

Strictly, the waist circumference is measured at a level midway between the lowest palpable

rib In vertebrate anatomy, ribs () are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the thoracic cavity, enabling the lungs to expand and thus facilitate breathing by expanding the ...

and the

iliac crest The crest of the ilium (or iliac crest) is the superior border of the wing of ilium and the superolateral margin of the greater pelvis. Structure The iliac crest stretches posteriorly from the anterior superior iliac spine (ASIS) to the posterio ...

. This is the definition used by the World Health Organization. Practically speaking, the waist is usually measured at the smallest circumference of the natural waist, usually just above the belly button. Where the waist is convex rather than concave, as in pregnancy and obesity, the waist may be measured at a vertical level 1 inch above the navel. Some laypersons use the level at the navel, but this can lead to underestimates. When using an automated body scanner that produces a

point cloud A point cloud is a discrete set of data Point (geometry), points in space. The points may represent a 3D shape or object. Each point Position (geometry), position has its set of Cartesian coordinates (X, Y, Z). Points may contain data other than ...

, neither the bones nor the navel can be located from the scan itself. A commonly used definition is the circumference at 4 cm above small of the back (SOB), though this does not appear to be the best fit for the strict definition, and 2 cm above SOB appears better (in a sample of 106 women of different ages, heights, weights, and body shapes). Variables such as posture significantly influence the measurement of the waist, and therefore any measurements for a group need to maintain a constant posture between the subjects.

Waist–hip ratio

Waist–hip ratio is the ratio of the circumference of the waist to that of the hips. It measures the proportion by which

fat In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food. The term often refers specif ...

is distributed around the

Size and health

Waist size (waist

circumference In geometry, the circumference () is the perimeter of a circle or ellipse. The circumference is the arc length of the circle, as if it were opened up and straightened out to a line segment. More generally, the perimeter is the curve length arou ...

) is an indicator of

abdominal obesity Abdominal obesity, also known as central obesity and truncal obesity, is the human condition of an excessive concentration of visceral fat around the stomach and abdomen to such an extent that it is likely to harm its bearer's health. Abdominal ...

and is one of the criteria for diagnosing the

metabolic syndrome Metabolic syndrome is a clustering of at least three of the following five medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein (HDL). Metabolic syndro ...

. Excess abdominal fat is a risk factor for developing heart disease and other obesity related diseases. A study published in the '' European Heart Journal'' in April 2007 showed that waist circumference and waist–hip ratio (defined as waist circumference divided by hip circumference) were predictors of cardiovascular events. The

National Heart, Lung, and Blood Institute The National Heart, Lung, and Blood Institute (NHLBI) is the third largest Institute of the National Institutes of Health, located in Bethesda, Maryland, United States. It is tasked with allocating about $3.6 billion in FY 2020 in tax revenue t ...

classifies the risk of obesity-related diseases as high if men have a waist circumference greater than and women have a waist circumference greater than . Further, waist circumference seems to be a better predictor of adverse health outcomes than the

body mass index Body mass index (BMI) is a value derived from the mass (Mass versus weight, weight) and height of a person. The BMI is defined as the human body weight, body mass divided by the square (algebra), square of the human height, body height, and is ...

(BMI). For example, those who lift weights may have high BMI but are at relatively low risk for cardiovascular consequences. For these people, waist circumference may be a better indicator of overall health. Some research suggests waist circumference can be predicted from

brain The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...

function, therefore capturing the neurobehavioral pathophysiology of obesity. An extremally high waist circumference can lead to falsely low estimates of bone health when using the

trabecular bone score The trabecular bone score is a measure of bone texture correlated with bone microarchitecture and a marker for the risk of osteoporosis. Introduced in 2008, its main projected use is alongside measures of bone density in better predicting fracture r ...

Society and culture

Fashion

In modern clothing, the region referred to as the waist is considerably below the waist as defined anatomically. With the advent of pants and skirts that do not require support from above, the clothing waist moved down to a position where the body starts to expand to form the buttocks and a support is therefore available. However, the waist region remains a highly important measurement and anthropometric landmark in garment construction.

Jewellery Jewellery (or jewelry in American English) consists of decorative items worn for personal adornment such as brooches, ring (jewellery), rings, necklaces, earrings, pendants, bracelets, and cufflinks. Jewellery may be attached to the body or the ...

, such as a belly chain, may be worn around either the clothing or anatomical waist.

Waist reduction and training

Waist reduction or waist training refer to the act of wearing a

corset A corset /ˈkɔːrsɪt/ is a support garment worn to constrict the torso into the desired shape and Posture correction, posture. They are traditionally constructed out of fabric with boning made of Baleen, whalebone or steel, a stiff panel in th ...

or other constricting garment to reduce or alter the waistline. The four floating ribs may be permanently compressed or moved by such garments. A girdle may also be used to alter the appearance of the waist. Waist reduction may be used simply to reduce the width of the waist. This change can be permanent or temporary. Waist training may be used to achieve a certain permanent waist shape, such as a pipe-stem waist.

History

Etymology

Definition: "middle part of the body," also "part of a garment fitted for the waist, portion of a garment that covers the waist" (but, due to fashion styles, often above or below it), probably from Old English 'growth', hence, 'where the body grows', from Proto-Germanic (cognates: Old English , Old Norse , Swedish , Old High German 'growth, increase', Gothic 'stature', Old English 'to grow'.

References

External links

*
Measured average height, weight, and waist circumference for adults ages 20 years and over (U.S.)
{{Human regional anatomy Abdomen Secondary sexual characteristics