Your doctor or healthcare provider is the best source to help you determine if you need to lose weight. Your doctor may use the Body Mass Index (BMI) chart or a weight calculator for kids, similar to the height/weight/BMI calculator on our site. What is Body Mass Index, or BMI? BMI is weight/(height)2 which is your weight divided by your height times itself. For example, if you weigh 135 pounds (59 kg) and are 5 feet tall (1.52 meters) :
your BMI = weight/(height)2 = 59/(1.52)(1.52) =25.4
Does a BMI of 25.4 mean that you are overweight? In adults a BMI over 25 is considered overweight. But in kids the overweight BMI number is not the same as in adults, and is not even the same for kids of different ages. Therefore, doctors use what is called the BMI percentile chart. The BMI percentile chart works for all ages and avoids having to have a separate BMI chart for each age child. Your BMI percentile shows how your BMI compares to other kids your age and sex. For example, if your BMI is 25.4 and you are 12 years old and female, your BMI is 94th percentile. That means your BMI is 94th compared to 100 typical kids your age and sex. Why is BMI percentile important? Because BMI percentile is related to health risks.* And most importantly, the overweight and underweight BMI percentile values are the same for all ages.
*Guidelines of the American Medical Association Committee on Overweight in Children and Adolescents.Therefore, in the above example if you are a 12 year old girl with a BMI in the 94th percentile you are, "overweight.".
How is BMI is related to health risks?
Our calculator uses the most recent height, weight, and BMI charts for kids ages 2 - 20 from the United States Center for Disease Control. If your BMI is 5th to 84th percentile, then your weight is in the healthy range for your age and sex. If your BMI is greater than the 85th percentile, which means your BMI is greater than the BMI of 85 out of 100 typical kids your age and sex, then you are "overweight". If your BMI is above the 94th percentile, then you are "obese", according to health experts.
If your BMI is above the 85th or 94th percentile, your doctor may recommend a diet or exercise program to keep your weight at the same level, so that as your height increases you will "grow into" a healthy BMI range. If you are at the age where you have stopped growing in height, or you are very overweight, your doctor may recommend that you lose weight. Children, especially if they are still growing, should not attempt to lose weight except under the supervision of a doctor or dietitian. Losing too much weight in growing children, or losing it too fast may hurt growth in height as well as hurt normal body development. Too rapid weight loss at any age can also cause other health problems such as gall stones.
If your BMI is below the 5th percentile for your age, then you are considered "underweight." Being underweight is dangerous because it can hurt growth in height as well as normal body development. Some kids think that they are overweight when they really are not. These kids may have an incorrect body image. They believe they are fat even though they are a healthy weight or even very thin. They are afraid of gaining weight. They often try to lose weight when they do not need to, and they can become severely underweight. Losing weight because of an incorrect body image can lead to a disorder called anorexia nervosa. Anorexia nervosa is an illness that usually occurs in teenage girls, but it can also occur in boys. Anorexia is very dangerous. It is essentially self-starvation. Anorexia can permanently harm a child's or teen's growth and development, and in extreme cases anorexia can result in death.
Anorexia and excessive overeating are both "eating disorders." They are not just problems with food or weight. They are an attempt to use food or weight to deal with emotional problems. Psychological counseling is therefore often recommended for kids who are either excessively overweight or anorexic.