Almost 70 percent of the kids were exposed to antibiotics before age two with an average of about two prescriptions per child.
By age two, 23 percent of the kids were overweight or obese for their age, which rose to 30 percent at age three and 33 percent at age four.
The more times the children had been exposed to antibiotics at a younger age, the more likely they were to be obese later on. Obesity was specifically linked to broad-spectrum antibiotics, like amoxicillin or tetracycline, not narrow-spectrum antibiotics like azithromycin. (Broad-spectrum means the antibiotic acts against a broad range of disease-causing bacteria.)