Factors That Affect Breast Shape and Size - Reasons Why Breasts Appear Different

Updated March 17, 2018

Breasts come in all shapes in sizes. Round or perky, tiny or huge, the varying contours of different breasts can be admittedly fascinating. What makes breasts so different from each other? Here's a roundup of the main factors that affect a woman's breast size and shape:

1. Body Fat

Female breasts, technically known as mammary glands, basically consist of milk ducts, lobes, and glands surrounded by fat. Weird as it is to accept, it is this fat that gives breasts their characteristic shape, texture and size. Women have larger, softer breasts than men (yes, men have breasts too) mainly because the female hormone estrogen tells the body to deposit fat in the chest area while testosterone makes men build more muscle. Women who have more fat will also tend to have larger breasts than those who have little fat. Fluctuations in weight and body size will affect breast size too - rapid weight loss will make the breasts smaller (and cause stretch marks too) while weight gain will give you larger mammaries. Of course how much fat tends to be distributed to the chest area depends on other factors - mainly, genetics.

2. Pregnancy

Childbirth is ultimately what mammary glands are built for. That is why pregnancy has one of the most significant breast-changing effects. With levels of the hormones progesterone, estrogen and prolactin flooding a woman's body, breasts become fuller and increase in cup size as fat deposits increase and the milk ducts enlarge. It even becomes fuller when a woman starts to lactate. Some women refuse to breastfeed their newborns based on the belief that the increase in breast size associated with nursing will make their breasts sag and droop. Recent scientific studies, however, have shown that breastfeeding does not adversely affect breast shape.

3. Age

beautiful old woman Photo credit

In addition to fat content and pregnancy, age is another factor that significantly changes how breasts appear, too. During puberty girls start to develop breasts as estrogen levels start to increase and more fat becomes stored in the chest area. Breast development continues until about the age of twenty. After that age breast shape and size becomes more dependent on other factors like fat content and pregnancy. By the age of forty, though, connective tissue (called Cooper's ligaments) that supports the breast start to lose their strength. Skin also starts to lose its elasticity, and supportive skin proteins like collagen and elastin that help support the breasts start to break down.

By the time a woman reaches menopause, these simply halt production. Gravity takes over, and by the age of sixty sagging breasts are a common (and perfectly natural) phenomenon. Some studies have suggested that wearing brassieres during puberty and under non-strenuous circumstances may actually weaken the Cooper's ligaments and lead to their atrophy. To keep the breasts' natural support, some doctors recommend wearing bras only when strenuous activity is involved (ie, sports and exercise) and during pregnancy.

4. Heredity

beautiful old woman Photo credit

Don't expect to be big-breasted if you come from a family of small-chested women. Genes and heredity play a big role in how a woman's breasts appear in two major ways. First, it determines how fat will be stored in the breasts. People store fat differently in their bodies, with some storing more fat on the belly or hips than the chest, and this is still a phenomena not clearly understood. What is clear though is that our body's genes play a big role in determining where fat will be stored, and these genes are passed in from generation to generation. Another impact of genes on breast shape is more indirect - genetic predisposition to being underweight, overweight or obese will affect body size, which in turn will affect breast size too.

5. Smoking

woman smoking Photo credit

This is a surprising fact, but smoking can and does make breasts droop and sag. Cigarettes contain compounds that break down elastin, which is the protein responsible for keeping skin supple. In the chest area, it helps support the breast as it keeps the skin more "tight" and together. Without it, breasts are more prone to the effects of gravity, and will eventually sag.

6. Surgical Enhancement

More and more women go under the knife to change the appearance of their breasts. Whether it is to make it bigger, rounder, and perkier or to reduce it in size, cosmetic breast surgery definitely changes breast appearance. Not all breast surgeries, however, are all done out of vanity - some diseases require women to alter their breasts surgically. Women with malignant tumors in the breast have to go under the knife too to keep the cancer from spreading. Different types of fibrocystic breast disease may also require breast surgery. 

It is important to take note regardless of its aesthetic appeal, breasts serve one important evolutionary purpose - to provide valuable sustenance to the young. So big or small, perky or not, a breast is basically just a gland with an important biological purpose.


007 Breasts. 007 Breasts, 2011. Web. 8 January 2011.

"Breastfeeding Shown Not to Adversely Affect Breast Shape." The Medical News. News-Medical.net, 2 November 2007. Web. 8 January 2011.

"Breasts - Structures and Types." Medindia.net. MedIndia, n.d., Web. 8 January 2011.

"What Gives the Breast Its Shape?" Mentorwwllc.com. Mentor Corporation, 2009. Web. 8 January 2011.

Photo Credit for Primary Image:

bra_sizes.jpg. Ibsrpo.net. Web. 24 January 2011.