In Children, Teens and Adults, Waist Circumference is the Best Indicator of Overeating, Overweight, or Obesity

You may have been to your doctor’s office and saw a table of “ideal weights.” These tables were constructed by the Metropolitan Life Insurance company over sixty years ago. This system classifies individuals by their “frame” size: small, medium and large. Trying to estimate “body frame” is often more opinion than fact. Most weight loss specialists have turned to the body mass index (BMI) or waist circumference as a more reliable indicator of weight status.

  • BMI is a measure of body fat. It is calculated by dividing the weight by the height squared. Since the formula is in the metric system, the formula needs to be corrected for pounds and inches.
  • Waist Circumference is measured with an ordinary tape measure around the belly button.

BMI Formula Calculation

Calculate BMI by dividing weight in pounds (lbs) by height in inches (in) squared and multiplying by a conversion factor of 703. Example: Weight = 150 lbs, Height = 5’5″ (65″)
Calculation: [150 ÷ (65)^2] x 703 = 24.96

For adults it’s simple. Either use this complicated formula or use our BMI Calculator. Our BMI tool automatically interprets the data for you. There is also a handy chart for your reference. Remember this can only be used by men and women over the age of 17. The formula is different for children. Their special BMI chart is below the chart for adults.

Definitions of Obesity, Overweight, Overeating, and Normal BMI in Adults and Older Teens

The National Institutes of Health provides the following BMI definitions.

Normal Weight: BMI between 18.5 and 25
Overweight: BMI of 25 to 30
Obesity: BMI of 30 or greater
Morbid Obesity: BMI of 40 or greater

For example, a woman who weighs 160 lb. and is 5 feet, 3 inches tall has a BMI of 28 (overweight). If she weighs 180 lbs. her BMI would be 33 (obese). A male who is 5 ft 10 and weighs 200 lb. has a BMI of 28 (overweight). If he weighs 220 lbs. then his BMI would be 32 (obese). The CDC has more information on assessing your BMI.

Using Waist Circumference to Tell if a Child, Teen or Adult is Normal, Overeating, Overweight or Obese

I have found that measuring waist circumference with a simple tape measure is an accurate, simple, and a non-threatening method to determine  overeating or overweight. The fat around the belly, and thus the waistline, is the most important determinate of medical complications from excess eating. It is a more biologically relevant measurement based on risk factors, and it is not influenced by height or large muscle mass. It’s just a simple measurement requiring only a tape measure. Focusing on waist circumference instead of total body weight permits you to determine in a few seconds which members of your family are normal, overeating or overweight.

Children with a waist circumference greater than the 95th percentile are obese, and above the 85th percentile are overweight. The 80th percentile is represented by the green line on the figure below. Children having a number above the purple line and below the green line are overeating. You can plot your child’s waistline and age on the graph below. Find you child’s age on the bottom and follow the line up until it intersects with his waistline on the left.  A “normal” child’s or teen’s waistline falls on the purple line or below in the graph. An overeating child or teen has a value above the purple line and below the green line. A child or teen is overweight or obese if his value falls above the green line.

In adults you need to consider gender. In general, for women a waist line > 34 inches and for a man > 40 inches indicates overeating, overweight or obese. A quick method to differentiate overweight and obese is to add 2 inches to each value. Thus for women, 37 inches is overweight and more than 39 inches is obese.

chart to determine whether your child or teen is overweight or obese

Using the Belly Button Number to Recognize Overweight/Obese vs. Overeating in Children, Teens, Young Adults

A simple formula for recognizing overeating or overweight is to find the Belly Button Number of each child. The Belly Button Number is the child or teen’s age + 17. If the waistline you measure is greater than the belly button number, then the child or teen is overeating. If it’s greater than the belly button number + 3, then he or she is overweight.

* Overeating Child or Teen: The waist circumference (in inches) you measure is greater than the child’s belly button number. (belly button number is age + 17)

* Overweight or Obese Child or Teen: The waist you measure is greater than belly button number +3 (or child’s age +20)

For example, Jack’s Belly Button Number is his age of 13 years + 17 or 30. Since his waist circumference was greater than his belly button number, Jack was overeating. In fact, his waist circumference exceeded his Belly Button Number by 3. Therefore, he is not only overeating but probably overweight. His height is 4 ft 10 inches, giving him a BMI of 25.8 which is the 93rd percentile.

Changing the eating habits of children who fall into the overeating category will prevent them from gaining excess weight and developing future problems. Don’t rely on your pant size. Many people, especially overweight adult men, wear their pants below their waist and have a big belly flopping over their belt. To measure waist size (circumference), place a tape measure around your bare abdomen just above your hip bone. Be sure that the tape is snug, but does not compress the skin, and is parallel to the floor. Relax, exhale, and measure. As in turns out, waist circumference in children is a better indicator of the metabolic disorders accompanying weight gain and the associated risks than the scale or BMI.

Changing Waistlines in Growing Children and Teens

The normal child increases his/her waistline about 1 inch per year. However, normal weight gain depends on the age and gender of the child. Here are the normal weight changes for children as they mature:

* Boys: Between the ages of 6 to 11, the average boy gains about 6 lbs. per year and the rate doubles from age 13 to 16 to 12 lbs per year.

* Girls: Between the ages of 6 to 8, girls normally add about 6 lb. per year. At 10 years old, body weight increases by about 10 lbs. per year, until age 14 when the weight gain slows down a little.

You can see how difficult it is to recognize overweight and obese children given ever-changing normal values, and how easy measuring the waistline becomes.

If your child is between 5 to 7 years of age, you may have noticed a rapid weight gain. This is normal. This time period is called the adiposity rebound. It corresponds to the time when fat cells start to increase in number. Prior to this, fat cells increased or decreased in size, not number. This adiposity rebound can last any where from 3.5 years to 5 years. Your overweight child or teen increases his weight at a greater rate than normal weight children. It’s important for you to look at the waistline measurement as a trend instead of focusing on individual numbers.

What You Should Do if You Find Your Child is Overeating or Overweight?

The first step is not to single the child or teen out from other members of the family. Start by only changing his or her food or beverage intake. Often a few simple food or beverage changes are all that are needed. For example, if the child is only overweight, stop the purchase of soda, Gatorade and fruit juices for the whole family. No one really needs these sugar filled drinks. This simple change can prevent a 10 lb. weight gain over the next year.

In growing children and teens, overeating or overweight are treated the same. The first goal is to slow down the rate of weight increase so that by growing taller and maturing, the child or teen will “grow into” his weight. For Jack, just reducing his overeating will permit him to achieve a normal weight by the time he is 15 years old. The decision to take action does not need to be complicated or difficult. Identifying the problem is easy, and as you will see, doing something about it is just as easy. But remember, the whole family makes the same changes. No one is singled out or treated differently. In fact, the most successful “diet” is when no one even recognizes there is a “diet” to begin with. Bad foods and drinks and trips to McDonald’s simply disappear.

Set an Example for Your Children to Follow

Role modeling, setting the example, is the first order of business for parents who suspect their child or teen is overeating or overweight. If the parent’s diet revolves around burgers and fries, 20 oz. bottles of soda or juices, Häagen-Dazs ice cream and bags of Doritos or Cheetos, what can you expect from children and teens? It’s important to set a good example for your kids, not only in eating, but in biking, running, walking and swimming.

Using Waist Circumference and BMI in Adults

The waist circumference measurement is also easy and useful for adults. A waistline greater than 40 inches for men and 35 inches for women correlates with the critical amount of fat within the abdomen. Ideal waistlines are 32.5 inches for women and 35 inches for men (at average heights). Below is a summary of the BMI and waist circumference values critical for the diagnosis of weight disorders in adults. They can be used for teens who are 16-17 years or more.

BMI vs. Waist Circumference Determines Obesity or Overweight