Breast density is defined by fibroglandular tissues and fat. In some women, the fat composition takes about 75 percent of the breast, according to Breastlink. As weight loss occurs, the size of the breast also reduces. The decrease in the size of the breast is dependent on how much body fat a woman loses, and of course, this is unique with each person.

Sagging breasts when losing weight is common. "If you keep stretching and shrinking something, it will wear out, like a sweater," said Stephanie Middleberg, a nutritionist, according to Cosmopolitan. However, sagging and breast size reduction can be avoided.


- Keep wearing supportive bras when you work out, but also when you're not on the treadmill. "A good rule of thumb for fuller-sized women is to reevaluate every four months, especially if it's a bra you're wearing super frequently," said Michelle Lam of True&Co, a retail company, according to Today. "With a B or C cup, you maybe not need to replace that bra for 18 months or more. If your nipple is sagging below the horizontal mark - they should be pointing out like headlights - then it's time. The spandex in the cup has given out. And once you've gotten to the tightest hook and it's still stretching out, it's time to get rid of that bra."

- Don't do crash diets that tend to make you lose weight faster, but in an unhealthier way, which can affect your skin's collagen and elasticity. Instead of going on crash diets, stick with a low-glycemic carb diet, so that even as you slowly lose the pounds, your body is still processing natural sugar that limits collagen loss, according to Prevention.

- Do push-ups and bench presses with dumbells to improve muscle tone. "Working the chest from multiple angles with enough weight ensures plenty of stimulus to increase strength and develop the muscles," said fitness expert Comas Keck, according to Women's Health. "This can add beautiful shape to the chest."

- Consider hydrotherapy, an ancient form of medical treatment, according to the Science Museum. While taking a shower, focus the stream of warm water on your breasts for a few minutes, then rinse with cold water for 20 seconds. This supposedly aids in the circulation of the blood around your breasts, thus making the skin firmer.