The body mass index, or BMI, provides a free, easy-to-use tool for assessing your weight. However, individual variables affect the accuracy of body-mass-index calculations. It's helpful to consider BMI in the context of other health and body -at indicators when evaluating weight-related risk factors and setting weight and activity goals.
Significance
Body mass index is generally comparable to direct body-fat assessment methods, including underwater weighing and dual energy x-ray absorptiometry, according to the Centers for Disease Control and Prevention. The body mass index is a useful tool in estimating body fat and categorizing individuals as underweight, normal weight, overweight and obese. However, because body mass index is calculated using only height and weight, it doesn't take into account individual variables relating to body composition, such as muscularity.
Factors
In addition to height and weight, your age, sex and lifestyle affect your ratio of muscle to fat. These factors can contribute to errors in body-mass-index estimates. For example, normal-weight obesity may go undetected if BMI is the only tool used to assess health risks associated with body fatness. Even if BMI estimates indicate normal weight, individuals with an unhealthy level of body fat are at increased risk for heart disease, Reuters reports.
Variables
Factors not taken into account by the body mass index include variables related to muscle mass. As you age, for example, muscle mass decreases while body fat increases. The body mass index is not gender-specific, meaning that it doesn't take into account that women generally have a higher percentage of body fat than men. Another variable that affects the reliability of BMI is increased muscle mass resulting from a physically active lifestyle. Athletes and other highly fit individuals tend to have less body fat than individuals of comparable size.
Considerations
Although BMI helps identify whether an individual is overweight or obese, other factors are also important when assessing body weight. You should take waist circumference into account, as well as weight-related risk factors such as high blood pressure and inactivity. For the most accurate weight and body fat screenings, consult your doctor. If your weight is outside the normal range based on BMI, implement a weight-management plan that incorporates healthy diet and regular exercise. Even if your weight falls in the normal range, regular exercise is key to building and maintaining a healthy muscle-to-fat ratio.
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