"DXA measures the amount of fat tissue more directly than BMI," says Hillary Burdette, M.D., nutrition specialist at The Children's Hospital of Philadelphia and lead investigator of the study, which appears in the March issue of the American Journal of Clinical Nutrition.
This distinction is important, say the researchers, because adiposity, rather than weight, is thought to account for obesity-related illnesses, such as type 2 diabetes, high blood pressure and sleep apnea, among others. "With the rising prevalence of childhood obesity, interest has increased in determining whether breastfeeding or the delayed introduction of complementary foods - or both - can reduce the risk of later obesity. We found no such effect," says Dr. Burdette.
Dr. Burdette emphasized, however, that the team's findings in no way diminish the importance of breastfeeding for multiple benefits to mothers and children, including protection from infection and establishing a bond between mother and infant. The American Academy of Pediatrics recommends that infants be exclusively breastfed until at least four months of age.
The researchers used DXA to measure the body composition, particularly the fat tissue, of 313 Caucasian and African American five-year-old children. They had previously gathered information on breastfeeding, infant formula use and the timing of the introduction of complementary foods from the children's mothers when the children were three years old. The researchers defined complementary food as anything other than breast milk, formula or water. They asked mothers when their children started drinking juice or eating infant cereal, baby food or table food.
The research team found no significant difference in fat mass between children that were ever breastfed and those never breastfed. Children who were breastfed for a longer duration and those who were breastfed without concurrent formula feeding did not have significantly lower fat mass than did those children who were never breastfed. Children also did not differ if they were introduced to complementary foods before or after four months of age.
It has been suggested that children that are exclusively or predominantly breastfed for the first four months of life have a different growth pattern than children who are not fed breast milk for the first four months of life. In this study the researchers found no difference in fatness between these two groups of children at 5 years of age. 
