The latest research show that 54 million Americans with BMI in the range of overweight or obesity have good test results, what implicates that there is no heart disease or diabetes. On the other hand, Americans with normal BMI have worse results. This could be the beginning of the end of this commonly used indicator.
Body mass index (BMI) is a factor derived by division of body weight in kilograms by the square of height in meters. Classification of BMI was developed for adults only and cannot be used in children. Designation of the body mass index is important in assessment of the risk of diseases related with overweight and obesity, for example, diabetes, coronary heart disease, atherosclerosis. Increased BMI is associated with increased risk of development of such diseases.
It all started in the United States with proposal of the Equal Employment Opportunity Commission (EEOC). Proposition was to charge staff with costs up to 30% of the health premium, if they do not meet the criterion of “health” understood i.a., as reaching a certain Body Mass Index (BMI). The aim of the scientists was to determine whether BMI really indicates our health. They focused particularly on cardiovascular diseases and diabetes. The study group involved 40 420 people aged 18+. The volunteers were subjected to the following medical procedures: blood pressure measurement, tests on triglyceride level, cholesterol, glucose, C-reactive protein, and insulin resistance.
Research showed that more than half of people with overweight, 29% obese and 16% of obese type II / III, have good test results and 30% with normal BMI do not. Conclusion is very simple: BMI is not an appropriate indicator of health. Moreover, previous studies of the same group of researchers have not shown a clear association between weight loss and improvement of studied health indicators such as blood pressure, blood glucose, triglycerides, or cholesterol. Therefore, healthy people with abnormal BMI would be unfairly burdened with additional costs for the health insurance.
In another research scientists paid attention to limited value of BMI as obesity indicator. It is only an indirect measure of body fat in comparison with more direct bioelectric impedance. In addition, BMI does not necessarily reflect changes that occur in the body with age. It is clear that fat tissue increases, and muscle tissue decreases with age. Both, sensitivity and specificity turned out to be weak.
In short, the use of BMI as obesity indicator can cause problems of misclassification, which may lead to significant abnormalities in estimation of the effects associated with obesity. On the other hand, responsible people from EEOC need to consider consequences of their action based only on BMI. Scientists should seek constant improvements of diagnostic tools related to weight.
There is still a widespread opinion that BMI is an indicator of a healthy weight. As it turns out, good BMI is not always associated with health. It can be a dangerous phenomenon when people with a good BMI, who are convinced that they are of normal weight, neglect prevention, what might be connected with the development or late detectability of diseases.
Written by: Paulina Rudzka, Monika Klimek, Marta Misztal
Source:
1. A J Tomiyama et al. Misclassification of cardiometabolic health when using body mass index categories in NHANES 2005-2012,International Journal of Obesity, doi:10.1038/ijo.2016.17
2. K J Rothman, BMI-related errors in the measurement of obesity, International Journal of Obesity (2008)32,S56–S59; doi:10.1038/ijo.2008.87
3. Dr Claudia Langenberg et al.,Long-Term Risk of Incident Type 2 Diabetes and Measures of Overall and Regional Obesity: The EPIC-InterAct Case-Cohort Study, doi:10.1371/journal.pmed.1001230
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