Waist

The waist is the part of the abdomen between the bellybutton and breasts. On proportionate people, the waist is the narrowest part of the torso.

Waistline refers to the horizontal line where the waist is narrowest, or to the general appearance of the waist. People who diet are often said to be trying to "improve" their waistline.

Women tend to have narrower waists than men.

Fashion
The waistline of clothing generally corresponds to the human waist.

Traditionally belts are worn around the waist.

Jewelry, such as a belly chain, may be worn around the waist.

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 is distributed around the torso.

A waist-hip ratio of 0.7 for women and 0.9 for men have been shown to correlate strongly with general health and fertility.

Hip and buttock padding is used by some males who cross-dress as females to increase the apparent size of the hips and buttocks to resemble those of a female.

Waist Measurement
The size of a person’s waist or waist circumference, indicates abdominal obesity. Excess abdominal fat is a risk factor for developing heart disease and other obesity related diseases. The National, Heart, Lung and Blood Institute (NHLBI) classify the risk of obesity related diseases as high if: men have a waist circumference greater than 102 cm or 40 inches, and women have a waist circumference of 88 cm or 35 inches.

A study published in The European Heart Journal April 2007 showed waist circumference and waist-hip ratio were predictors of cardiovascular events.

Waist reduction and training
According to a study, women waistlines have grown by 2 inches in the last 10 years from an average of 31.8 inches to 33.5 inches due to sedentary lifestyle.

Waist reduction or waist training refers to the act of wearing a corset 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 and inhibits one's ability to breathe well.

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.