Breasts can be confusing. Some people gained two whole cup sizes overnight the minute they hit puberty. Others only experience weight loss in that area. Why is that? "Genetics make up so much what determines our breast size," says Sherry A. Ross, MD, a women's health expert and the author of She-ology. "It's just so individualized, how our breast increases or decreases over time." With that in mind, we asked both Ross and Jessica Shepherd, MD, to break it down for us and list out the common things (besides implants) that can affect our breast size.
See what they had to say below.
1. Weight Gain/Loss
Both Ross and Shepherd say that no specific food can increase or decrease the size of your breasts; it's more about weight loss and gain. "Breast tissue is primarily made of fat," says Shepherd. "Changes in weight … can reflect changes in breast size." Ross says people used to think that eating more estrogen-rich 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," she says.
"During sex, the increase in arousal, sensation, heart rate, and blood pressure will increase blood flow to the breasts, which will cause them to swell," says Shepherd. "There is some evidence that breasts can swell up to 25% in size during sex because of this increase of blood flow." But before you think that having consistent sex will require a shopping trip, Ross says this increase is temporary. "It's going to increase in that moment because blood is being stimulated. Once it's over, it will go back to its normal state," she says.
"With the increase in activity and decrease in body fat, there may be a decrease in the breast fat tissue for athletes," says Shepherd. Ross says that exercise increases muscle and specifically tones the chest wall, where the breasts sit, and could potentially help keep them lifted.
4. Birth Control
"The changes are usually because of fluid retention or temporary weight gain," says Shepherd. Ross says that some will experience stimulation in the breasts that will cause them to go up a complete cup size.
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"As estrogen and progesterone levels fluctuate near ovulation, there is an increase in blood flow to your breasts—this can increase their fullness and also cause tenderness," says Shepherd.
6. Menstrual Period
According to Ross, so much of breast size changing is driven by hormonal changes. So when it's that time of the month, you experience your breasts feeling fuller because of the estrogen’s effect on the breast tissue.
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According to Ross, when you have unsupported breast tissue, it causes the breasts to sag. "Some people say that when you smoke, there is less oxygen in your cells. That can affect your tissues in general," she says.
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Ross says we experience a decrease in breast size during menopause because we lose our estrogen. "When we lose our estrogen, we lose our breast tissue," she says.
This article was originally published at an earlier date and has been recently updated.