Exercise, but not fanatically. Excessive exercise has been linked to a drop in estrogen levels[3], although regular exercise has also been linked to drops in estrogen levels as well.[4] The difference is while normal exercise is healthy — and might decrease the risk of breast cancer in women[4] and overall longevity[5] — excessive exercise may not be. The increase of estrogen levels due to reduction is exercise is simply not worth it.
Athletes may experience a drop in estrogen levels. This is because women with low levels of body fat have more trouble producing estrogen.[3] If you are an athlete or have very low body fat levels, see your doctor for an appropriate response to replenishing your estrogen.