Determining A Healthy Body Weight
Body Mass Index
Body mass index (BMI) is a common measurement used to asses body weight; it is also an indirect but reliable way of gauging a person’s body fat level. BMI is determined from your weight and height. Here’s the formula for calculating it:
• BMI = weight (in pounds) divided by height (in inches, squared) and multiplied by 704.5
For example, here’s how a woman who weighs 130 pounds and is 5 feet 4 inches tall would determine her BMI using the formula:
1. Convert height to inches: 5 feet x 12 inches per foot = 60 inches; because the woman is 5 feet 4 inches, add 4 inches; height in inches = 64
2. Multiply answer from #1 by itself: 64x 64 =4096
3. Divide answer from #2 by 130: 4096 / 130 = 0.0317
4. Multiply answer from #3 by 704.5 to get BMI: 0.0317 x 704.5 = 22.36 = BMI
After you know your BMI, you can see which of the following weight categories it falls in:
• Underweight – BMI below 18.5
• Normal weight – BMI 18.5 – 24.9
• Overweight – BMI 25.0 – 29.9
• Extremely obese – BMI >= 40
Although BMI can be a useful estimate of a person’s body fat level, it has some weaknesses; it might overestimate body fat levels in those who have a lot of lean body mass and are muscular, and it might underestimate body fatness in those who are older and have lost muscle mass.
BMI-for-age is used to determine weight status in children. Because body fatness changes as children grow, and because girls tend to have more body fat than boys, gender and age are used to determine BMI values. Pediatricians and registered dietitians can asses children’s BMIs to determine whether their body weight falls within a normal range or whether they are at risk for obesity or overweight.
Measuring your waist size is useful in both adults and children. Having more abdominal or visceral fat can increase your risk for diet-related diseases including cardiovascular disease, high blood pressure, and type 2 diabetes.
Waist circumference measurements are especially useful for those whose BMI is less than 35; for some populations, waist circumference helps predict the risk of chronic illness better than BMI.
Here’s how to measure your waist circumference using a simple tape measure:
1. Place the tape measure snugly (but not tightly) around the bare abdomen just above the hip bone; make sure the tape measure is parallel to the floor.
2. Relax, exhale, and then measure the waist in inches.
As your waist circumference increase, so does your risk for cardiovascular and other diet-related diseases; those especially at risk include:
• Nonpregnant women with a waist measurement greater than 35 inches
• Men with a waist measurement greater than 40 inches
Eat to Beat Disease
Using a tape measure periodically to keep track of your waist size is a great way to determine how you’re doing in terms of body fat level and body fat distribution.
Although there are no established norms for waist circumference in children, those who measure above the 90th percentile are more likely to have heart disease risk factors such as higher levels of triglycerides and lower levels of HDL or good cholesterol, as well as obesity-related diseases and conditions.
Overweight and Obesity
A pediatrician can monitor your child’s waist circumference (measured at the end of the lowest rib after your child has taken a normal breath) at her annual checkup as part of an overall health assessment.
Visceral fat, also known as abdominal fat, is fat that accumulates around internal organs. This fat is more dangerous than other types of body fat because it’s believed to secrete potent hormones and other chemicals that increase the risk of cardiovascular and other diseases.