Does your body mass index (BMI) suggest that you need to lose weight or register in a local weight loss program? For decades, BMI has been regarded as the standard tool in determining the amount of body fat of an individual, based on the ratio of the person’s height and weight. The BMI of a healthy individual has been determined to be within the range of 18.5 – 24.9 and values higher than this range indicate that an individual is overweight or obese and thus needs to lose weight. A BMI value of 30 and higher is generally associated with obesity, also suggesting the need to lose weight.
The application of the principle of BMI in identifying obesity has fueled various types of health programs that are focused on weight loss. To lose weight, it is important to include fruits and vegetables in every meal. These natural food items are rich in fiber and antioxidants, addressing not only weight loss goals. It is also helpful to include a regular exercise in one’s weight loss program to burn the excess body fat that is often associated with obesity.
Despite the importance of the BMI in weight loss programs and obesity, a recent report has shown that the use of BMI may result in false-negative results for people who are actually dealing with obesity. In a study conducted from 1998 to 2009 involving approximately 9,088 subjects, the amount of body fat was measured using two approaches, namely BMI and dual energy x-ray absorptiometry (DXA). The DXA approach makes use of an x-ray machine that measures body fat, together with bone mass and muscle volume. The number of individuals classified as overweight and obese using each approach was then compared in terms of level of sensitivity in detecting weight problems.
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The results of the study showed that the BMI approach classified 26% of the study participants in the obesity group, whereas the DXA technique identified 64% of the same study population as having issues with obesity. In addition, 39% of the study population was classified by the BMI approach as non-obese, while these same individuals were categorized by the DXA technique under the obesity group. The most alarming finding of the report involved the larger error rate among women who needed to lose weight. The study showed that 25% of the male study participants and 48% of the female population were wrongly diagnosed by BMI as without obesity, while DXA classified them as obese. Given these false-negative results, it is possible that individuals would think that there is no need for them to lose weight or enroll in a weight loss program when they actually do.
This latest study may serve as a direct demonstration that BMI alone cannot be used in determining whether an individual needs to lose weight in order to control obesity. The occurrence of false-negative results using the BMI approach indicates that there are now individuals who think that they have normal body weight when they might be actually classified as overweight or obese using a more sensitive measurement system such as the DXA.
Another factor that influences the error rate of the BMI approach is that it simply employs height and weight measurements in computing for the total amount of body fat of an individual. The calculated BMI then determines whether an individual needs to lose weight by engaging in a weight loss regimen. It is important to understand that certain people have bigger bones and thus they will definitely weigh more than another person of the same height but with smaller bone structure. At the same time, the individual with the smaller bone structure may have more body fat but this will never be detected by using the BMI approach since only the height and weight measurements are used in the calculation.
This new study shows that BMI is not the only basis in determining the extent of obesity in a population and the results suggest that the incidence of obesity in the United States might be worse than previously described. Weight loss programs have heavily relied on BMI values and thus there may be a need to reassess methods in determining whether an individual needs to lose weight
It is also interesting to determine whether BMI can still be used in the elderly when it is known that bone loss at this advanced age often results in a decrease in height and possibly, weight as well. The use of the DXA approach might be more reliable among the elderly because it specifically scans the amount of bone, muscle, and fat in the body. Weight loss programs can then be designed based on the results of the DXA examination.
As for us who think that we have normal BMIs, well think again. It might be possible that we also need to lose weight and thus let’s start thinking of increasing our intake of fruits, nuts, and vegetables as a regular component of our meals for our own personal weight loss program.