CBS Local — A new study says that overweight toddlers can begin showing signs of heart failure as early as their first birthday. Researchers in Romania noted that obese children had already developed distinct differences internally compared to babies at a healthy weight.

Physicians at the Constantin Opris hospital in Baia Mare say they studied over 400 children from a few months old to teenagers. The study found the obese children had a heart muscle that was 30 percent thicker than children at a healthy weight. The enlarged heart is reportedly an early warning sign of future heart trouble.

“It’s a huge problem because obesity and being overweight affects growing numbers of children and it’s possible that this thickening could lead to heart failure in time,” said lead researcher Dr. Delia Mercea. “When obesity exacerbates their heart health in toddlerhood, alarm bells should be ringing,” warned Tam Fry of the National Obesity Forum in Britain.

According to the study, nearly all of the overweight babies were bottle-fed instead of breast-fed. The discovery is raising concerns that formula milk could be fueling higher obesity rates. “We should encourage healthy food and physical exercise. Doctors should tell parents what kind of food to give to children,” Dr. Mercea added.

The CDC says one in five children in the United States are obese. The number has reportedly tripled since the 1970’s.