Will weight loss cause a change in focal density on a mammogram?

Depends: With the breasts being a fat storage site, a weight change may alter the mammographic density of the breast. This change may necessitate additional evaluation of the breast to ensure that this is not a cancer.

Usually not: Losing weight can reduce the overall fat content of the breast tissue but this will cause a generalized increase in breast density that should be seen on both sides.

Weight loss will: affect the breasts just like other parts of the body: fat content will decrease. Since the fibroglandular components(i.e. the dense parts) stay the same, the ratio of dense tissue to less dense fatty tissue will increase, and the breasts will appear more dense on mammo. This will be a generalized effect, not focal, however.