We hate to deliver depressing news, but the fact is, some breast sag is inevitable. Having a baby, breastfeeding, and racking up more birthdays all contribute to a loss of elasticity of collagen, the connective tissue under the skin, leaving your set more deflated than firm. Sag can also be a matter of genetics. If your mother had a droopy pair, you might be predisposed to one, too (thanks, Mom!). Here's the thing: Some boob behaviors that seem like they have nothing to do with sag can actually contribute to it, so if you avoid them, your breasts will be better off. And considering that a recent UCLA study found that breast tissue ages two to three years faster than the rest of your body, you might want to quit any habit linked to a flaccid pair—like these. Crash Dieting Cycling back and forth between the same five to 10 pounds probably won’t make a dent in your set. But yo-yo dieting 30 or so lbs over and over? Definitely. Each time you gain and lose weight, breast tissue becomes more slack, kind of like old tights, says Michael Edwards, M.D., a breast surgeon and president of the American Society for Aesthetic Plastic Surgery. Smoking Even your breasts can’t escape the damage cigarettes do. “Any amount of smoking weakens and ages skin by decreasing the blood supply to the skin surface,” says Edwards. Skipping Sunscreen Exposing your face to UV rays without a protective coating of sunscreen-can lead to premature wrinkles, and it has the same effect on breast sag by stretching out collagen and damaging skin, says Edwards. Wearing an Unsupported Bra Whether it’s the boulder holder you wear during the day or the sports brayou change into at the gym, not sporting proper support is a big reason for droop. “The more your boobs bounce around, the more stressed breast skin and collagen become,” says Edwards. Stop in a lingerie shop and ask for a fitting just to make sure you’re wearing the right bra for your shape. High-Impact Workouts The research is scant right now, but some experts say that the back-and-forth repetitive motions that happen when you run or do a similar workout can lead to a breakdown of breast collagen. Source