What Is BMI & Fat?

Your weight includes many different components within your body. Fat is one of them, but there's also bone, water and muscle to name a few. One way of assessing if you have a healthy body weight is to evaluate your percent of fat as well as your body mass index, known as BMI. Body fat and BMI have been used to assess disease risk and overall health.

Fat Facts

We need fat. Fat is a necessary type of tissue in our body that assists in a variety of ways. Fat protects our organs and bones. Without fat's cushion, we would easily bruise and damage other parts of our body. Body fat rounds out our shape and keeps the body warm at an ideal internal temperature. It helps the body transport fat-soluble vitamins, like vitamins A and E. Fat also provides a storage of fuel for the body, breaking down into energy between times of eating.

Where's the Fat At?

The trick comes in keeping fat balanced to a safe and acceptable amount. Not having enough fat can put the body at risk for long-term damage and even death. But having too much fat puts strain on the body's skeletal system and organs, resulting in a higher risk of health problems.
Fat distribution can help determine if one's fat level is safe. For women, a high percentage of body fat is carried in the hips and thighs as a protective mechanism for having children. They also carry more fat in their chest and at a higher percentage throughout their body for hormonal reasons.
The first area to be concerned with extra fat is around the belly, for both men and women. Having extra fat here has been correlated with higher heart disease risk. Apple-shaped people tend to have more problems with abnormal cholesterol and blood pressure levels than pear-shaped people who carry their weight further down around their hips, butt and thighs.

Keeping Fat In Check

Diet and exercise help keep body fat levels healthy. Eat a calorie range that is right for you to avoid storing too many extra calories as fat. An excess of fat coming from food as well as simple carbohydrates, like sugar and white flour, can quickly get stored for later use if your body doesn't need it for fuel.
Exercise helps burn off any extra fat storage to keep the body lean. Remember that you can't target burning fat from one particular place, so use a workout that incorporates the entire body for maximum energy burn and muscle development.

BMI Explained

BMI, short for body mass index, is a measurement and screening tool that describes weight in relation to height. It does not measure fat directly but helps describe how a person's weight is proportionate to her stature. BMI information is used to determine health risks of an individual and larger populations. Having a BMI in the overweight and obese categories has been associated with having a higher risk of the following diseases: heart disease, type 2 diabetes, certain cancers, high blood pressure, abnormal cholesterol levels, strokes, sleep disorders, osteoarthritis and some gynecological problems. For this reason, clinicians encourage people to keep their BMI in the normal range.
While BMI is noted as a "reliable indicator of body fatness for most people," by the Centers for Disease Control, it doesn't reflect true health risk for all types of people. Using BMI as a health indicator has been criticized by some because it does not account for muscle mass, bone density or unique factors like pregnancy. A full evaluation should be done by a clinician to determine if an unhealthy BMI score truly indicates a greater health risk. Also factors like sex, race and age should be taken into consideration and can point to normal variations in BMI. But BMI is a helpful, easy-to-use tool for research purposes to get a broad perspective on a large group of people's health risk assessment.

How To Find Your BMI

The formula for calculating your BMI is weight in pounds divided by the squared value of height in inches and then multiplied by the conversion factor of 703. A quick BMI calculator is also available from the the Centers for Disease Control (see Resources)
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A normal BMI score falls between 18.5 and 24.9. Below 18.5 is considered underweight, and above 24.9 is in the overweight category. A person is considered obese when his BMI lands at a score of 30 or higher. Children and teens should be given special consideration when evaluating BMI scores. There is a unique calculation for them that helps account more for their age and appropriate ranges for their age group.
Keep in mind that a BMI reflects a general assessment and does not always tell the whole story about what's right for your body. Ask your physician if you think your BMI might be indicating a greater health concern for you.