Running in essence doesn't shrink your breasts, Norris says. ... “So if a person is training and eating well and they're reducing their overall body fat, it's reasonable to think they could also decrease their breast size because they're decreasing fat in their breasts,” she says.

Does running give you a flat chest?

Vigorous exercise such as running has a number of positive effects, including the opportunity to lose overall body fat. If you're wondering whether you'll get a flatter chest as a result of your efforts on the treadmill, the answer is yes -- as long as you're not overindulging.

How can I run without losing my boobs?

If you are doing cardio regularly, you will lose both muscles and fat from your breasts. It is important that you must focus on strength training which in turn builds chest muscles. This will help in maintaining perfect breast size.