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Armpit fat can result from weight, genetics, and other causes. Exercises that build muscle in your chest wall and upper arms may help reduce its appearance.

Take a quick walk anywhere people are exposing their arms, and you’re bound to see some extra folds of skin and tissue, or what some people call armpit fat.

People of all weights, ages, and sizes can have extra fat around their chests and underarms. Tight clothes can also push skin up from the chest, giving the appearance of armpit fat.

Whatever its cause, armpit fat is completely normal.

Read on to learn about the causes of underarm fat and what you can do to reduce its appearance if it’s something that bothers you.

Armpit fat can occur in people of any gender. It appears to be more common in women than in men.

Tops or bras that are too tight can cause the skin between the breasts and armpits to spill out.

But aside from clothing choice, armpit fat has many causes. Here are just a few of the most common causes.


Body fat distribution is largely determined by heredity and genetic factors.

One large study found that dozens of genetic factors may determine where you store fat. This study also found that fat accumulation and distribution in people with vulvas is more likely to be impacted by genetics than in people with penises.

If you have relatives who have armpit fat, you may be more likely to have it, too.


If you’re overweight, fat may deposit in or under your armpits. It’s largely up to genetics where excess fat gets stored.

If you have excess weight, subcutaneous fat may deposit in your underarm area. Weight gain can also make your breast and armpit area larger.

Losing weight by eating a nutritious diet and exercising can help reduce armpit fat. But studies show that it’s hard to target or spot-reduce specific areas of the body.


Breast tissue is very sensitive to hormonal changes associated with puberty as well as pregnancy, menstruation, and menopause.

Alterations in the production of estrogen and progesterone can cause breasts to swell. During pregnancy, prolactin, another hormone, enlarges the breasts as they get ready to produce milk.

These kinds of hormonal changes can increase the look of excess skin or fat in the area between the breast and underarm.

Axillary breast tissue

Excess breast tissue may also masquerade as armpit fat. This condition is known as axillary breast, or accessory breast.

Axillary breast is caused by the development of breast tissue outside of the normal breast area. It is most likely to occur in the axilla, or armpit.

Axillary breast is not common. Data indicates that this congenital condition occurs in approximately 2 to 6 percent of women and 1 to 3 percent of men.

Like all breast tissue, axillary breast tissue responds to hormonal fluctuations. Changing estrogen levels and progesterone may make armpit fat look thicker or lumpier during pregnancy or right before menstruation.

Lymphedema (swollen lymph nodes)

Lymph nodes are glands that can be found throughout the body. Lymphedema occurs when the glands in your armpits (the axillary lymph nodes) swell up.

Swollen lymph nodes can be caused by infection as well as arm or hand injury. Breast cancer and lymphoma are other potential causes.


Poor posture may not cause armpit fat, but can make it more apparent.

If you have a forward-rolling shoulder posture, standing up straight may help reduce the look of extra armpit skin.

Here are some ways you can help remove or reduce the appearance of armpit fat:

  • Lose weight to help reduce armpit fat as well as fat stores throughout your body.
  • Build muscle mass in your chest wall and upper arms. Armpit fat can be resistant to exercise, including resistance or weight training specifically for that purpose. Building chest muscle mass and toning your upper arms can help tighten the area, reducing the look of armpit fat. Building muscle also burns calories, so it helps with weight loss.
  • Wear properly fitting undergarments. A new bra can help reduce the appearance of armpit fat. Many people don’t realize they’re wearing tight undergarments that can push the skin and fat around the sides of your breast upward.
  • Ask your doctor about surgical removal. If you have axillary breast tissue that affects your quality of life, your doctor may recommend liposuction to remove it. Liposuction is a common type of plastic surgery that removes soft fatty tissue from targeted areas of the body. Open excision may be recommended if there is an extensive amount of axillary breast tissue.

Armpit fat is not usually caused by a medical condition and not typically a cause for concern.

If you notice a change in your armpit, such as swelling or a lump, see a doctor. You should also seek medical attention if you have limited or reduced mobility in your arm. This may sometimes be caused by excessive axillary breast tissue.

If you feel distress about your appearance and wish to discuss your options for having armpit fat removed, don’t hesitate to seek medical support.

Armpit fat is a common occurrence in adults. It’s often caused by excess weight, but hormones and genetics may also play a role.

In some instances, armpit fat may actually be a condition called axillary breast. Axillary breast is breast tissue that grows in or near the armpit.

Talk with a doctor if excess breast tissue is disrupting your life.