When singer Mariah Carey developed gestational diabetes mellitus (GDM) before she delivered twins in April of 2011, she hoped giving birth would put her worries about diabetes behind her. A new study shows she might have done just that, because she breastfed the twins from April until July.

That's just enough time to give her protection from developing Type 2 diabetes for at least 15 years, according to a study from three German research centers.

It turns out that breastfeeding for at least three months affects a mother's metabolism, reducing metabolites that contribute to the development of insulin resistance and Type 2 diabetes.

Up to 9.2 percent of pregnant women in the U.S. develop GDM, but some don't breastfeed for even three months, much less for as long as the American Academy of Pediatrics (AAP) recommends. The AAP says babies should be breastfed exclusively for the first six months and then continue with supplemental food for at least a year or longer.

This protects baby from obesity and strengthens the immune system and helps mom avoid diabetes and certain cancers.

Because 60 percent of women with GDM eventually go on to develop Type 2 diabetes (and within the study population 50 percent developed it within 10 years), breastfeeding is a huge protection.

So whether you had GDM or not, try to breastfeed.