In an earlier article we explored BMR and the idea of using it as a tool for determining weight loss needs. Another  tool is widely used as well. It’s your BMI.

Just to recap, in the article about BMR the suggestion is that it be used as a guideline only, and that it be used  with a “fudge factor” of a few percent. This was because of all the variables involved in addition to the rigors of dieting according to BMR numbers. As a refresher, you can review that article by clicking here  Your  BMR to Lose Weight.

Having written about that tool, it seems appropriate to go into the facts and nuances of the BMI tool as well.

So now let’s explore some stuff about your BMI.

Just what is BMI?  The acronym stands for “body mass index”. Simply stated it’s a calculation to quickly determine how much weight you should lose to be at a healthy weight for your height.  The actual calculation is the result of dividing a person’s body weight by the square of his or her height.

You can use this handy tool provided by the CDC to find your BMI.

BMI For Adults

The formula was invented between 1830 and 1850 by a man named Adolphe Quetelet from whom it got the name “Quetelet Index for BMI.” The current popularity of the index dates from a paper published in 1972 by Ancel Keys in the Journal of Chronic Diseases.

You can read all about the history of BMI, controversies, etc.


It’s a good place to start but don’t go there without your slide rule in hand and your thinking cap firmly in place.

Ancel Keys’ studies documented BMI as being a good proxy for determining body fat percentages on a height/weight basis as pertaining to prosperous Western societies.

It’s important to note that Keys himself stated that BMI was appropriate only for population studies and not appropriate for individual diagnosis.

However, in spite of its being inappropriate for use when applied to individuals, its simplicity of calculation resulted in widespread application for use with individuals, both by the medical community as well as the weight loss industry. 

So inappropriate or not, use of your BMI is with us today. And, as with using your BMR to lose weight, there are factors and considerations to know about for using your BMI.


  • Age, while not directly a part of BMI calculations has an impact on your BMI. Older people have a natural tendency to store more fat. So a BMI for a 30 year old person would not be accurate for that same person at age 50 years. In addition, BMI numbers for children need to be interpreted in a different way than BMI numbers for adults.
  • Sex too has a bearing on BMI. Women have a natural tendency to store more fat than men. So a man and woman of equal height and weight may show both to have an ideal BMI, when in fact the woman, on a true body fat percentage basis, would be considered overweight.

Certainly that’s not good news for the ladies – – and unfortunately the news gets worse.

A study reported by the Mayo Clinic in May 2010 and published in the journal “Obstetrics and Gynecology”, concludes that BMI may not be accurate for women between the age of 20 and 33 years old. In the study, BMI failed to identify nearly half of the women in the study who were actually obese.

  • Race also has a bearing on your BMI. Large population studies have had to adjust healthy range BMI numbers to compensate for racial differences.
  • Muscularity impacts your BMI ratings. Take two people, a sedentary office worker and a body-builder. Assume they are of equal height and weight. Their BMI numbers will be identical, but one desperately needs to start losing fat and the other has no fat to lose.
  • According to the Center For Disease Control and Prevention (CDC) “BMI is a fairly reliable indicator of body fatness for most people. BMI does not measure body fat directly, but research has shown that BMI correlates to direct measures of body fat”. The words “fairly reliable”, “for most people”, and “correlates” mean we’re talking about something that will get you in the ballpark but may not be accurate for YOU.

You can read the whole CDC article



  • The first consideration for using your BMI is to fully understand that it is a measure of your total body weight regardless of the weight of your body’s individual tissue types. Fat, muscle, bone, organs, etc. all weigh different amounts for the same amount of physical volume. So your BMI could remain unchanged while the actual amount of your body’s building blocks change in relation to each other.
  • Another consideration is that relying on your BMI to determine your need to lose weight can result in your falling into a class of people shown by a recent (March, 2008) Mayo Clinic study as having “normal weight obesity”.

This is a situation where your BMI indicates you’re at a healthy weight, but your actual body fat percentage puts you at risk for type 2 diabetes and cardiovascular disease. You can read the Mayo Clinic report


This is a sobering report and needs to be taken seriously.

It’s basically saying that your BMI should not be your “be all, end all” determining factor in deciding whether to lose weight or how much weight you should lose.


Like BMR, your BMI is just a tool and a rather imprecise one at that. Use it guardedly as a rough guide. And if your BMI is anywhere close to a published boundary indicating that you are overweight,  don’t be complacent and don’t obsess over it either. Just start losing fat.

The right combination of diet and exercise is your best way to deal with your BMI. Your body wants to be healthy but it needs your help. Here’s a great way to help your body.

CLICK HERE – forget BMI – get help for PERMANENT fat loss.

 Please be sure  that before starting on any diet or exercise program, you  check with your physician first to get their concurrence and advice about your plans and goals. This is particularly important with regards to your BMI. Check with your physician to get their perspectives about your BMI relative to the Mayo Clinic findings and CDC position.

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