Okay, let's recap what we've learned about breastfeeding. We now know breastfeeding does not cause sagging breasts. That breastfeeding can help reduce a child's risk for developing allergies. Most what the information about breastfeeding is promoting the positive effects. However, it was announced today that breast milk may increase a child's obesity risk.

Dr. Maria Weyermann of The German Cancer Research Center in Heidelberg found that women who have high levels of protein secreted by lipids in their milk can pass this to her child. However, other researchers doubt that nursing can make a child overweight.

The significance of these findings remain unclear, Dr. Matthew W. Gillman and Dr. Christos S. Mantzoros, Harvard Medical School, Boston, point out in an editorial accompanying the study, because infants may not be able to absorb the adiponectin contained in breast milk.

Also, they add, high levels of adiponectin in adults actually reduce heart disease and diabetes risk, making it "counterintuitive" that high levels would contribute to excess weight in children.

The jury is still out on whether nursing does protect children from becoming overweight, Weyermann and her team add.

The researchers investigated how breast-feeding might influence obesity risk by looking at adiponectin and another protein secreted by fat cells, leptin, which regulates appetite as well as the body's use of energy from food.

Adiponectin is involved in metabolism of fats and sugars. The fetus and placenta produce both proteins at high levels, the researchers point out, raising the possibility that they play a role in fetal development.

The levels of both proteins were measured in the breast milk of the mothers of 674 children when the infants were six weeks old. Among the children who were breast-fed for at least six months, obesity risk rose in tandem with breast milk adiponectin levels. However, leptin levels showed no association with whether or not a child would be overweight.