Height is often the main factor used when determining a healthy weight; however, age is a strong factor taken into consideration when determining healthy weight for an important part of the population.
Body mass index (BMI) is a ratio of weight to height used to classify individuals into health risk categories taking into account weight and height for adults and age, sex, weight and height for children ages 2 to 20. Only BMI data for children and teens take age and sex into consideration, because in this age group the amount of body fat changes with age and differs among boys and girls.
Percentiles are measurements on a chart that show where a child is in regards to sex, age and height compared with other children. Children and teens are underweight if their BMI value in relation to their gender and age fall into the less than fifth percentile, healthy weight if between the fifth and 85th percentile, overweight if between the 85th and 95th percentile and obese if equal to or greater than the 95th percentile.
A weight-to-height ratio that predicts an overweight or obese percentile should prompt action for weight loss, but a weight loss regimen should not be considered before consulting a physician. Factors such as hormones, genetics and environment all influence height and weight. The doctor will take all these factors into consideration and make necessary recommendations for action from there.