The average healthy weight for children at the age of 3 is 25.5 to 38.5 pounds for boys and 27 to 38.5 pounds for girls, explains the Centers for Disease Control and Prevention. Body mass index is the major tool in determining the healthy weight of children, teens and adults.
Obesity in children can cause serious health issues that affect a child's mental, physical and emotional state. Sleep apnea, breathing problems and joint discomfort are associated with childhood obesity, according to the CDC. It can have an adverse affect on a child's self-esteem, and obese children are more likely to carry these issues into adulthood. A balanced nutritional diet helps keep children healthy.