But new research suggests that chemicals called phthalates, which are found in the plastics that pacifiers and toys are typically made of, may be linked to higher rates of obesity in children.
The chemical, called di-ethylhexyl phthalate (DEHP), is suspected of being able to alter biological functions involved in fat metabolism. In the study, children with the highest DEHP levels had nearly five times the chance of being obese compared with those who had the lowest DEHP levels.
How could a chemical used to soften plastics trigger fat development in a child?
"It may trigger the master regulator of fat creation and lipid metabolism," explained study co-author Dr. Mi-Jung Park, a pediatric endocrinologist and professor at Inje University College of Medicine, in Seoul, South Korea.
DEHP may do two different things that increase fat development, Park said. It may reduce the effect of androgen -- a male sex hormone -- which lowers body-mass index (BMI). It may also disrupt thyroid function, which plays a role in weight gain. Interfering with androgen or thyroid hormones can affect appetite or a person's rate of metabolizing food, she explained.