Ideal Body Weight: What does it mean?
Most people choose their ideal body weight (IBW) number as their long term weight loss goal. Ideal bodyweights can be found on Body Mass Index Charts (BMI), which are widely used by health professionals, allied health professionals, fitness enthusiasts, and those just looking to shed a few pounds. But, what does that IBW number mean?
Ideal body weight charts originated from an extremely old index (mid 1800s old) called the Broca Index. Standard body weight was determined by subtracting 100 from body length in centimeters. The BMI chart was later developed from the Broca Index. The BMI was and still is determined by dividing one’s weight by height. Scientists originally used these charts to study and compare the health of populations with respect to their weight.
Nuts and Bolts
A pattern was noticed between certain weight ranges and deaths. Low body weights seemed to correlate with tuberculosis and pneumonia which were the leading causes of death at the time. Remember, this originated in the mid 1800s. Medical professionals concluded that individuals of higher weight would fair better with respect to those common illnesses. This was critical information to have in order to possibly improve quality of life. It was especially important for those in the business of insuring a person’s life. This is why the Metropolitan Life Insurance Company and others, created height and weight tables. Today, these tables are still used to identify healthy weight individuals and individuals with weights that are “unhealthy” a.k.a. correlated to higher death rates. The ideal body weight ranges have evolved over time due to new science concerning poor health conditions associated with higher body weights. In essence, a person’s body weight was used by medical professionals and insurance companies to gauge one’s health/insurability.
BMI Isn’t For Everyone
There are a few drawbacks to using the BMI chart of today. It’s important to note that the standard tables were based on adults between the ages of 29 and 59. So it should not apply to children. Another fine print note is that one inch should be added to your height, because the chart took into account individuals wearing one inch heeled shoes at the time. Yes. Seriously. Lastly, the lean body mass verses fat mass is not accounted when using either chart.
I would recommend that one NOT use the BMI chart if they are:
- Adult non sedentary person (Athlete/Bodybuilder/Fitness Enthusiast…):
These individuals have more muscle on their body than fat, and because muscle by volume weighs more than fat, the BMI chart is not going to be accurate gauge. Since BMI is determined by weight and height, more muscle on the body will cause an individual to have a high BMI. Body fat percentage is a much better tool to use in this instance. (Learn Why Your Body Fat Percentage Has Nothing To Do With Your BMI)
Medical professionals encourage a slightly higher BMI for the elderly to help combat osteoporosis. The theory is that a little bit more body weight challenges bone structure, making it stronger. The elderly are also encourage to strength train for this same reason.
The BMI chart is not designed for children. Perhaps this is the beginning of another evolutionary period of the BMI chart to address the increasing risks of childhood obesity.
The Bottom Line
So what then does IBW mean? Generally speaking, for sedentary adult persons, it means that if you are in a healthy weight range on the chart, you are less likely to suffer from death compared to someone lighter or heavier than you.
1. Czerniawski, M. (2007). From Average To Ideal: The Evolution of the Height and Weight Table in the United States 1836-1943. Social Science History Association. DOI-10.1215/01455532-2006-023
2. The Annals of Pharmacotherapy. (2000). The origin of the “ideal” body weight equations. http://www.theannals.com/content/34/9/1066.full.pdf
3. US National Library of Medicine. (2013). Body Mass Index. http://www.nlm.nih.gov/medlineplus/ency/article/007196.htm
4. Wikipedia.com. Broca Index. http://wikipedia.qwika.com/de2en/Broca-Index