What You Should Know About BMI (Body Mass Index)

By Theresa Halvorsen

Why Does BMI Matter?

Your BMI is your body mass index. The BMI is a better indication of potential weight problems than simply looking at the weight of an individual. The BMI takes your height and weight into consideration and is a reliable indication of the amount of body fat. However, the BMI does not actually measure body fat. If your BMI is high, your doctor will use other measurements to see how much body fat you actually have.

BMI and Athletes

Since the BMI uses weight to determine the amount of approximate amount of body fat, people with high quantities of muscle may be heavier than their low-muscled counterparts, making their BMI higher. However, athletic people don't usually have high quantities of body fat. Check with your doctor if you're an athlete and your BMI is very high--chances are, you're just fine.

BMI and Children

Experts use the same criteria in determining the BMI (body mass index) in children and adults; they look at the height and weight of the child. However, experts also consider different criteria. With children, they look at age and sex along with height and weight, since the amount of body fat differs with age. In addition, the amount of body fat differs with girls and boys, especially as girls hit puberty.

How Do You Calculate BMI?

Square your height in inches. Take your weight and divide it by your height in inches squared. Multiply that number by 703. If this seems too complex, find a chart that does the work for you or speak to your care provider. When given your height and weight, your care provider should be able to calculate your BMI.

What Do All the Numbers Mean?

If you're BMI is under 18.5, you're considered underweight. BMIs from 18.5 to 24.9 are normal. If your BMI ranges from 25.0 to 29.9, you're overweight. If you're BMI is over 30, you're obese. Being overweight or obese increases your chances of hypertension, type-2 Diabetes, stroke, sleep apnea, some cancers and heart disease. When calculating your BMI, keep in mind that women tend to have more body fat than men, older people tend to have more body fat, and athletes have higher BMIs.

For more about this topic, and all things health and fitness, check out livestrong.com/eat-well/.

About this Author

Theresa Halvorsen has a BA in psychology and is a Certified Childbirth Educator (ICCE). She spent two years as a health educator for Kaiser Permanente and worked as a clinical specialist for UC Davis, teaching about health issues. Theresa has written about a variety of topics for LovetoKnow.com and HowtoDoThings.com.