With the number of people who are overweight or obese continuing to grow, body composition analysis is gaining more traction as the best measure of assessing health based on body size. Unlike weight or body mass index (BMI), body composition analysis looks at the percentage of fat mass and fat-free mass a person is carrying to gauge whether a person should be classified as underweight, normal weight, overweight or obese.
Understanding Body Weight, BMI and Body Composition
Body weight, BMI and body composition are all assessments of body size, but they're not created equal! Here's what you need to know:
Body weight is the most commonly used assessment of body size because it's so easy to measure and track. Face it, almost everyone has a bathroom scale in their home! The ease of measuring body weight is quite possibly its greatest benefit, but body weight is not the best predictor of health. This is because weight only provides a measure of how gravity works on a mass. It can be affected by hydration, menstrual cycles, food intake and more. Body weight cannot provide information about what's going on inside the body, but it can be helpful when used as a general guideline as long as it's not being perceived as a true indicator of health.
Body mass Index (BMI)
BMI is a slightly better assessment of health because it's used to predict "normalcy" based on height and weight. While it's still only moderately correlated with body fat percentage and markers of disease, one added benefit is that it removes the obsession some people associate with the scale. It's extremely easy to calculate BMI online using a BMI calculator, but it's also relatively easy to calculate by hand, as long as you know your height in meters and your weight in kilograms:
Calculation: BMI= Body mass (kg) / Stature (meters squared)
Unfortunately, BMI still doesn't provide real information about body fat percentage or body fat distribution, which can lead to problems. It is possible for a person with a healthy body fat percentage to be considered overweight or obese, based on BMI, and it's also possible for a person with an unhealthy body fat percentage to be considered normal weight, based on BMI.
Body composition is analyzed and predicted in a number of ways, each with pros and cons. The real benefit of looking to body composition analysis rather than weight or BMI is that it takes into account percentage body fat and body fat distribution, both of which are strongly correlated with markers of disease.Some methods of analyzing body composition are just as simple as measuring body weight and BMI, but these tend to be slightly less accurate than the more difficult methods of analyzing body composition. All-in-all, if you have the opportunity to track your health and fitness progress based on body composition rather than weight or BMI, you should take advantage of the opportunity to do so.
Understanding Body Fat
Fat gets a bad wrap. The fact is, people need fat. It provides fuel for movement, cushions the bones, joints and organs, provides warmth, carries vitamins and minerals and even helps depress appetite. Everyone needs a certain amount of body fat just to survive!
When you test for body composition, you're basically assessing how much fat you have in your body, how much of that fat is storage fat, how your fat is distributed and how these factors compare to markers for disease. Based on this assessment, your body fat percentage and distribution can more accurately place you into an underweight, normal weight, overweight or obese category.
Essential fat is the fat you must have in your body to perform basic human functions. This is the fat found in the heart, lungs, liver, spleen, kidneys, intestines, muscles and lipid-rich areas of the brain and spine. Women have an additional amount of essential body fat termed sex-specific essential fat. This extra essential fat plays a part in hormone regulation and child bearing, and can be found in the breasts, pelvis, hips and butt. In order to ensure essential fat reserves are maintained, minimal leanness standards typically recommend that men maintain no less than 3% body fat, while women should maintain no less than 10 to 12% body fat. While there are exceptions to this rule, women who become leaner than 10 to 12% body fat may start seeing disruptions to their menstrual cycle that could contribute to other health problems like bone mineral loss and stress fractures.
Storage fat is the fat that a person carries in excess of essential fat. Carrying storage fat is normal and healthy as long as you don't carry too much! This fat is carried primarily in adipose tissue, although it also accounts for the visceral fatty tissues that protect the organs in your abdomen. Healthy men and women carry a similar amount of storage fat (12% and 15%, respectively) in addition to essential fat reserves.
Healthy and Unhealthy Levels of Body Fat
Generally speaking, the acceptable standards of fatness for men and women are 20% and 30%, respectively. This means that men who have greater than 20% body fat, and women who have greater than 30% body fat are at a higher risk of heart disease, diabetes and other related diseases than individuals who maintain a lower body fat percentage.
Distribution Plays a Role
While total fat percentage is important, how it's distributed can also predict risk of disease. Individuals who carry more fat around their abdomen (the "apple" shape) are at a higher risk of heart disease, stroke and diabetes than those who carry fat in their hips, buttocks or thighs (the "pear" shape). Unfortunately, where you tend to gain weight can be genetic, so if you tend to put on weight around your waist, tracking your waist circumference with a tape measure can help you monitor your risk of disease. The American Cancer Society (ACS) considers a healthy waist size for women to be less than 30 inches, while men should keep their waist size below 35 inches. These numbers are lower than the numbers suggested by the American Heart Association, but according to a study performed by the ACS, for every four-inch increase in waist circumference above their sex-specific recommendations correlated with a 25 percent greater risk of death.
There are a number of different analysis methods. Depending on how accurate you want your body composition analysis to be, you can opt for home-based or lab-based analysis methods. Home-based methods include those commonly performed at gyms and fitness centers that do not require extensive high-tech equipment. See How to Calculate Body Fat to learn what's involved in the different approaches, as well a the pros and cons of each.