Mothers who breast-feed their babies for at least six months tend to lose significantly more weight during the first year after giving birth than do those who feed their infants formula, according to new findings by UC Davis nutritionists. In a two-year study, women who breast-fed during the first year of their children's lives lost an average of 4.4 pounds more than did those who formula-fed infants from 1 month to 12 months of age, reports Kathryn G. Dewey, nutrition professor, in the American Journal of Clinical Nutrition. "Although the magnitude of this difference isn't great, it may have important implications with regard to the development of obesity in adult women," Dewey says. She believes the reason for the weight-loss difference might be linked to the hormone prolactin, an important regulator of lactation.