Breast size and weight training: Does weight training decrease breast size?

Hi Tom,

I’m 18 and I’ve been working out since I was 16. Over the past couple months, I’ve been working out everyday. I usually run or do Tae-Bo, free weights and about 15 minutes of crunches. I’m actually starting to get happy with the results, but the problem is my breast size is getting increasingly smaller. Everyone is telling me that if I stop doing the free weights and working my chest muscles, the reduction will stop. Is that true?


Well, there’s good news and bad news. The good news is you are losing body fat. Nice job! The bad news is that when women lose body fat, they lose body fat everywhere, including in the breasts. It would be great if you could selectively reduce fat from certain places on your body and leave it on others, but unfortunately you can’t control where the fat comes from.

How much you lose from the breasts compared to other body parts depends on your genetic endowment. The breasts are part glandular tissue and part body fat. The amount of glandular tissue is genetic and can’t be changed. The amount of body fat can be changed. If a woman has more glandular tissue than body fat, then the reduction in breast size with fat loss will be minimal. If a woman has more fat than glandular tissue in the breasts, then the reduction will be more noticeable.

There’s nothing you can do to prevent at least some size reduction when you lose fat. If you ever get a chance to look through the magazines at the fitness models, you’ll see that virtually 100% of the ones who don’t have implants are flat-chested. Same thing is true for ballerinas and any other athlete with extremely low body fat.

To compete successfully in fitness or bodybuilding, women must have extremely low body fat – like low teens or even single digits (that’s like having NO visible body fat whatsoever). Most women don’t need to go to these extremes to look good. A body fat level in the mid to upper teens is better than average. If you avoiding dropping below the mid teens in body fat %, you will prevent major reductions in chest size.

Actually, your friends misinformed you about the weight training. If anything, training with weights will make your entire upper body look better and it will not reduce breast size. It might even give them a slight “lifted” look because the muscles underneath the breasts will be more developed.

Sorry if this was bad news to you, but you should be happy and proud of your results because most people are having a difficult time losing fat and you are doing it successfully. It’s sort of a trade-off. My advice: keep training hard – I’m sure you look great and you’ll continue to look even better if you keep on hitting those weights!