This story caught my eye I'm not sure that it works for women though.
It seems that male soldiers in the German army are finding that one of their customary exercises is causing them to grow breasts – and only on one side. This made the news because the problem was so widespread in the batallion that did this specific exercise over and over that the causal link just had to be the physical motion.
The exercise I’m talking about? They would strike the left side of their chest with their guns over and over. The thought is that this somehow triggered a hormonal reaction that caused them to have an excess of estrogen and to grow a breast only on the side that was repeatedly hit with the gun over again.
Military doctors got involved and advised the leaders of the group to change their exercise because they thought there was a definite cause and effect relationship between the exercise and the fact that their soldiers suddenly had one-sided gynecomastia (this is the term used for male breast growth – see more here
http://www.breastnewsmagazine.com/male-breast-enhancement/).
There is no real explanation how mechanical hits like this could produce such dramatic shifts in hormones in only one side of the male chest, but it is thought that there is some mechanism which causes the shifts to higher body fat because the soldiers also happened to test with a higher overall BMI, which is the ration of fat to muscle.
Women typically have a higher ration of fat to muscle, it’s just in our genes unfortunately to have less muscle mass and more fat on our bodies than men. It is likely due to evolution and a woman’s need to nurture her young and give birth, and perhaps it even served yet another purpose going back centuries, for a survival mechanism in times of famine.
It is interesting that the men who did the gun-hitting exercise not only showed more left side breast growth than men in other batallions that did not have to do this exercise, but also had higher BMI readings than them. This insinuates that these men not only were more likely to grow breasts but also were more likely to have an overall higher BMI.
This has to be attributable to higher levels of female hormones, which in turn lead to a switching “on” of the higher fat cell content. After all, breasts are made of pure fat, and if this switch were turned on it makes sense the breast would grow bigger and the BMI would increase. It is still curious why this overall effect wasn’t translated into both pecs though, just one.
http://www.breastnewsmagazine.com/german-male-soldiers-growing-breasts-out-of-the-blue-on-one-side/