Increasing/Decreasing Breast Size: What You Need to Know


At times it can feel like we all feel dissatisfied with our bodies; those of us with straight hair wish it was curly. Those with curly hair do everything they can to tame it. Some women are discontent with their breast size. 

Yep, it can seem like the grass is always greener… and if our breasts were just a little bigger, or we could reduce breast size… then! Then, we’d be on the road to happiness…

To be clear, at Knix, we think there’s no one right size. Breasts come in all shapes and sizes and they’re all beautiful. That said, let’s understand what determines the size of your breasts and if there’s *really” anything you can do about it.

What Governs Breast Size? It’s In the Genes

Your breast size and shape is largely governed by your genes. In fact, this can influence not just the size, but also the shape of your breasts and of your nipples too.

According to Nature, “Breast size is a highly heritable trait. A twin study previously estimated the heritability of bra cup size to be 56%. Several genome-wide association studies have also identified common genetic variants associated with breast size.”


Another major factor that can be both nature and nurture is body weight. Breasts are complex body parts but they are composed significantly of adipose fat. This can mean that individuals with higher body fat will often have larger breasts.

What About Nutrition?

There is speculation about whether certain diets contribute to larger breast size. The American Journal of Clinical Nutrition studied connections between dairy intake and breast size, for example. And you’ll find countless Reddit threads citing supplements and diets that can increase or decrease breast size, from green tea to flaxseeds and everything in between.

In our research, there was no prevailing data to consistently claim a connection between certain food groups or supplements and breast size. If you consider taking a supplement or changing your diet with hopes of enhancing or reducing your breast size, please do consult with your doctor first. 

What Can Cause Breast Size to Change

While it’s not exactly easy to transform the shape or size of your breasts, they do change over the course of your lifetime. These changes are often driven by hormonal changes that occur over the course of a lifetime. 

Age: Puberty to Menopause

From puberty through maturity and into menopause, our bodies go through many changes. These developmental stages are often ushered in by hormonal changes and hormonal changes can definitely affect your boobs. 

Menstrual Cycle

Hormones also play a major role in your menstrual cycle and these can cause monthly changes to your breast size. Many women especially notice breast swelling and tenderness just before their period as part of their premenstrual symptoms (PMS) and/or during ovulation, around the middle of their cycle.

Hormonal Birth Control

Hormonal birth control is used to prevent unwanted pregnancy but the hormones in play can also cause fluid retention and breast swelling in some women. These effects are often stronger in the first few months of taking a new birth control pill.


During pregnancy, your breasts may double or triple in size. According to the Mayo Clinic,

“One of the first signs of pregnancy is an increase in breast size. As early as two weeks after conception, your breasts start to grow and change in preparation for producing milk. Stimulated by the hormones estrogen and progesterone, the milk-producing glands inside your breasts get bigger and fatty tissue increases slightly.

By the end of your first trimester, your breasts and nipples will be noticeably larger, and they may keep growing throughout your pregnancy. Breast enlargement accounts for at least a pound of the weight you gain while pregnant.”

Your breasts may remain enlarged for a while after birth.

What You Can Do to Change Breast Size

So, for the most part we’re not in control of any of the influencing factors listed so far… so is there anything you can do to change your breast size?

Quit Smoking

Among the many health risks associated with smoking is a loss in skin elasticity, which can affect the delicate skin and breast tissue. This can cause breasts to sag. Some women perceive this as a change in size, though it’s really more related to shape unless accompanied by other changes.

Maintain a Healthy Weight

Weight gain and loss is one of the many reasons it’s recommended you go for a bra fitting regularly (every year or so). This is because the fat component of a woman’s breasts can make it a body area she’ll experience weight gain or weight loss.

However, it’s worth noting that it is difficult-to-impossible to target body fat gain or loss to a specific body area. And if you’re a healthy weight, we definitely don’t encourage weight loss or gain simply to impact the size of your breasts. Remember, if you lose or gain weight it will be distributed throughout your body, affecting other areas as well as breasts.

Certain exercises can also add strength to your chest muscles, which may impact the perkiness of your breasts. 

Weigh the Pros & Cons of Breast Augmentation

Of course, one of the more obvious ways to change breast size is to go under the surgical knife. Whether it’s a breast augmentation or a desire to reduce breast size, this will cause a more extreme and often permanent change to your breast size.

Some women with larger breasts experience back and neck pain as a result of their breasts. So, while the reasons for breast augmentations can go beyond the cosmetic, we generally advocate discussing all the pros and cons with your doctor. 

Try Different Bra Styles

Different styles of bras promise to increase your cleavage, while others claim to minimize your breast size. It’s definitely worth trying different styles of bra to see what makes you feel most comfortable with your silhouette, and in your skin.

We strongly recommend getting properly fitted too — an ill-fitting bra can make you feel really out of sorts. The wrong size or fit of bra will ruin your day. You’ll feel uncomfortable, maybe even sore, and just want to get home so you can rip the damn thing off. 

At Knix, we really wanted to help more women avoid this experience altogether. As an online retailer, we know it can be especially daunting to make a bra purchase online. That’s why we developed our virtual fit program. Learn more about it today and book your appointment!

What to Expect from a Knix Virtual Fitting:

  • Book your virtual fitting here
  • We’ll connect you with one of our expert Knix team members for a 1-on-1 fitting session over video chat. 
  • For your bra fitting, we recommend you wear a bra with little or no padding and a fitted t-shirt to make sure we get an accurate measurement. You’ll also need either a) a soft measuring tape or b) a piece of string or cord and a tape measure or ruler.
  • With different styles and sizes for 30A to 42G in the world’s most comfortable and supportive wireless bras, our fit experts can help you get into something that you will love to wear every single day.

A Note from Knix

We all have certain hang-ups about our bodies and appearance. A lot of these come from unrealistic standards set by the beauty and fashion industries, which is something we actively work to change in our own approach to presenting our products.

Ultimately, we hope that in doing so the conversation can move on from “how do I change…” to “now I’ve started to embrace…” But obviously this is a very personal journey for every woman and the answer for one woman may not work for another.

Ultimately, it’s about your body and your journey! You know best :)