The FDA approved the new treatment for about 20 percent of breast cancer patients with a form of the disease that is typically more aggressive and less responsive to hormone therapy.

NPR: FDA Approves New Targeted Breast Cancer Drug

The animals also became more responsive to the hormone insulin, which controls the way the body uses sugar.

BBC: Type of body fat 'boosts health'

Researchers thought that only hormone-responsive breast cancers would be affected by breast-feeding.

NPR: Study: Breast-Feeding Decreases Cancer Risk