Breast milk contains a protein that could reduce the risk of obesity, according to US research.
A protein in breast milk could reduce the risk of obesity
A team at the Cincinnati Children's Hospital Medical Center found high levels of a protein, which affects the body's processing of fat.
They believe its presence in breast milk could influence a person's "fatness" later in life.
The findings were presented at the annual meeting of the Paediatric Academic Societies in San Francisco.
Researchers say this is the first step in understanding the relationship between breast milk and metabolism.
Dr Lisa Martin and colleagues found high levels of the protein adiponectin.
Adiponectin is secreted by fat cells and affects how the body processes sugars and fatty substances in the blood.
Low levels of this protein have been linked to obesity, type 2 diabetes, insulin resistance and coronary artery disease.
However high levels of adiponectin have been linked to lower rates of disease.
Dr Martin said: "Exposures early in life, during the period of extreme growth and development, may have an impact on adult disease."
They also discovered the presence of another protein in breast milk, called leptin, which also helps to regulate body fat.
However the levels of adiponectin were more significant than leptin.
But Dr Martin added it is still yet to be seen whether adiponectin has any 'biological significance'.
Dr Ian Campbell, Chair of the National Obesity Forum told BBC News Online: "We know there is a clear link between breast feeding and a reduced risk of obesity, but we are not sure why."
He said the risk appears to be lowered further the longer a child is breast-fed.
"There is an accumulative effect, the longer they are breast-fed the better it is.
Dr Campbell added that breast feeding also enhances immunity.
Rosemary Dodds, policy research officer for the National Childbirth Trust, told BBC News Online: "This study is interesting because it looks at the mechanism behind why breast-feeding may reduce the risk of obesity."
She said although the Trust is keen to promote breast-feeding, the decision is a very personal one.
"We support women to make a decision that's best for them" she said.