Does Weights Training Reduce The Size of My Breasts

By Giuliana Zegarra
Jan 14 2020
Will CROSSFIT® Reduce The Size of My Breast

Does Weights Training Reduce The Size of My Breasts

Women have a very intimate relationship with their breasts. Besides their primary function to produce milk to feed babies, breasts can define our identities and transmit messages about our health, mood and sexual desires. Some of you might even have given them names and treat them with tenderness or humor (depending on the day!). Yes, we think about them a lot, we love them and we care about them. But a woman’s relationship with her breasts is often much more complicated than just worrying about how they look.

For women dedicated to sports, the size of their breasts can be either an advantage or harm to their performance. For women wanting to get into physical activities having big breasts can discourage them from trying cardio routines or even a smooth jog around the neighborhood. Nobody wants to have sore breasts the day after exercising, right? What about women practicing/starting CrossFit? We get so many related questions: Are there any boob shrinking exercises? Do sports stunt breast growth? Does running reduce breast size? Let’s get to the facts and answer these questions once and for all.

I have no doubt that if you are enjoying CrossFit it’s because you love that mix of high-intensity workouts and strength training. This fabulous blend of movements have a great impact on your health and your community. Strength training is one of the quickest ways to lose fat. And yes there is a lot of chances that if you lose fat, your breast size may get smaller along with the rest of your body as it burns off fat.

But don’t get scared! Before jumping to conclusions, let’s take a closer look at what other factors are involved in a potential reduction of breast size when doing CrossFit or other kind of functional fitness and strength training.

Factors that have an impact on your breast size while working out

CrossFit can reduce your breast size — but only to a point and that’s because your breasts are made up of more than fat. They also contain lymph nodes, connective tissue and milk glands/ducts. Add to that your genetics and training routine. So yes, breast size is determined by a complex dynamic. There are different types of women exposed to different external factors that all together determine the sizes of their breasts. Let’s take a look at some of these factors to better understand how this reduction works:

Genetics and Breast Size

If we talk about the anatomy of the breasts, they are located in the chest wall over the pectoralis major muscle. They have 15 to 20 lobular glands that are surrounded by adipose tissue (fat) with little connective tissue (ligaments). Around 75% of the breasts are made up of body fat! As you know, there is a huge variation between women’s breast in size, contour and density. It’s very rare to find a woman with a symmetric pair of natural breasts (plastic surgery doesn’t count in this definition). Plus, we need to consider hormonal influences like menstruation, pregnancy, lactation, use of contraceptives and other hormonal supplements. All of these factors cause changes in the glandular components’ shape and structure. This article mentions that all these changes often require a change in bra or cup size. So, don’t worry if you notice some mild changes in your breasts’ size. It’s probably due to one of the factors mentioned above. However, if the changes are more than mild you should visit your doctor.

If we talk about genetics related to our breasts, we should also consider body fat. Each one of us has a different propensity to store body fat in certain areas of our bodies. Sadly, it’s impossible to lose body fat in only specific areas. When we are engaged in high intensity workouts as CrossFit, we tend to shed body fat all over. But again, the quantity and areas where we lose more fat differs from one to another. Some of us may lose more fat in our derrieres. Or some other may start losing fat in their thighs, bellies, and some women will lose some body fat in the breasts.

The truth is, it’s hard to know with certainty which part of your body will be more toned and how much fat you will lose in your breasts. This could depend on the composition of your breasts. Women with less body fat tend to have more dense breast tissue (glands, milk ducts and supportive tissue) and less adipose tissue (fat). When these kind of women lose weight, they might not notice a significant decrease in their breasts as a woman who has a greater proportion of fatty tissue in her breasts to begin with. If you want to know about the density of your breasts you have to take an imaging tests like a mammogram.

Does nutrition have a real impact on the size of our breasts?

It’s crazy how much information is available about this topic. Whether you want to increase or reduce the size of your breasts, there are tons of “magical” diets to make your wishes come true. But unfortunately, our breasts don’t work like that.  

Sherry A. Ross, MD, a women’s health expert and author of She-ology and her colleague Jessica Shepherd, MD. say that no specific food can increase or decrease the size of your breasts; it’s more about weight loss and gain. Jessica stated “Breast tissue is primarily made of fat, changes in weight can reflect changes in breast size”. To that Sherry adds that people used to think that eating more estrogen-types of foods (such as soybeans) could affect breast size, but she says it’s not true. “It’s really a function of the weight gain (or loss) as a result of the food you eat”.

Weightlifting and their impact on breast size

So, how does weight training affect breast size? When you strength train, you become stronger and build muscle, but you may also lose body fat. Lifting weights increases muscle tissue, which speeds up your metabolism so you lose fat. And as mentioned before, as you lose fat, there is a big chance that your breasts become smaller. Elite women athletes often get down to very low body fat and lose a significant amount of breast adipose tissue.

If you think about it, weight lifting won’t increase the size of your breasts, because they consist mainly of fatty/glandular tissue. Unlike muscle tissue, you can’t tone and firm fat. 

Melissa Crosby, M.D., associate professor of plastic surgery at the University of Texas MD Anderson Cancer Center also said “Your breasts sit on top of the pectoral muscles, but aren’t part of them so you can develop stronger muscles underneath your breasts without changing their size or shape“. So, if you focus your weight lifting in the pectoral muscles underneath the fatty tissue then, the circumference of your chest will increase slightly and your breasts will be pushed a bit forward. Plus, your posture will improve and all this will make your cleavage look a bit more prominent.

To summarize, it’s not that weight training directly causes breast tissue to shrink, it’s the loss of body fat, including fat within the breast tissue that causes the breasts to look smaller in size. In fact, if you have been doing CrossFit for some time, you may notice some shrinkage in the size of your breasts as well as loss of body fat and toned muscles. With high intensity and strength training such as CrossFit, you might experience a loss of glandular breast tissue in addition to loss of adipose tissue. That’s because excessive endurance exercise, can cause a drop in estrogen and that reduces the glandular component of breast tissue. So while there are now miracle exercises to make boobs smaller, overall fitness will likely tone up your body fat content which is a good thing!


In conclusion, yes, by doing CrossFit there is a big chance to lose the fat in our breasts and therefore the need to go buy smaller bras. But at the end, how much your breasts will be reduced depends on your genetics. I know this might sound discouraging in your pursuit of getting healthier and better at CrossFit and I totally get it, women are attached to their breasts in a very special way. That’s why I was very touched when I read all the positive comments about this topic in our Barbell Beauties FB group.

Women like you and me, who, through their journey in CrossFit, have seen their bodies getting fitter and their breasts smaller but now they are embracing these changes with love and respect (and tons of humor!). And that’s the message I want to pass to you. Forget about stereotypes. You are in charge of your body and you are working hard to accomplish your own goals. Your body is a smart machine that will adapt to perform for success. Keep rocking in everything you do! 

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