29 Aug How to Determine Your Ideal Body Weight

Ideal body weight is a tricky topic to discuss and define.  If your weight is higher than ideal but a large portion of your weight is muscle, is that a problem?  No.  Is there a way to determine ideal body weight?  Is weight even the best metric to follow ?

The 3 most commonly used methods to determine ideal body weight:

1.  Actuarial tables

2.  BMI (Body Mass Index)

3.  % Body Fat

I.  Actuarial Tables

MetLife has the most widely accepted actuarial tables.

Actuarial tables have several limitations.  While the tables consider frame size, sex, and height, as the height of an individual deviates greater than average, the tables become less accurate.  These tables do not consider body composition as well.  Using elbow width as an indicator for frame size has not been proven to correlate with muscle or bone mass, but kudos to MetLife for trying.  Truth be told, most people never measure their elbow width, they just guess their frame size.  Most people also don’t realize that when using the tables the height measurement used is the height of an individual wearing 1″ heel shoes. The weights used also assume that you are wearing approximately 3 pounds of clothing.

II.  Body Mass Index

The most widely method used is Body Mass index, otherwise referred to as BMI.  No fancy equipment is needed.  All you need to know is your weight and your height.  You then plug those values into a program, look the result up on a chart, or calculate it using the formula below.

1.   Multiply your height in inches by your height in inches. (I know it sounds crazy but just trust me.)

2.  Divide your weight by the result from Step 1.

3.  Multiply the result in Step 2 by 703.

Here is the formula written out. [Weight lb. / (Height in. x Height in.)] x 703  = BMI

A typical BMI chart looks like

Now the big question is, “What in the world does that mean?”

The National Institutes of Health (NIH) has issued the following BMI guidelines:

BMI of 19 or below: You’re considered underweight.

BMI between 19 and 24.9: You’re in the healthy range.

BMI between 25 and 29.9: You’re considered overweight.

BMI of 30 or greater: You’re considered obese.

BMI of 40 or greater:  You’re considered morbidly obese.

While BMI is easily obtainable and does give good predictive information for the non-athletic person, it does not distinguish muscle from fat.  In muscular individuals % Body Fat is a much better predictor of “healthiness.”

Another less commonly recognized problem exists with BMI.  Some normal weight individuals will have a normal BMI but have a high %Body Fat.  This is otherwise known as the “Skinny fat syndrome.”  See my post for more details on this topic  http://www.nuvitalityhealth.com/2-belly-fat-truths/

III.  % Body Fat

There are multiple ways to determine % Body Fat.  Each has it advantages and disadvantages.  Here are the top Four:

1.  Skin Calipers – This technique uses calipers to measure the thickness of subcutaneous fat at several locations.  These measurements are then placed in a formula to calculate total body fat.  This is most commonly used technique used in gyms.  The technique is highly user dependent.  You can buy a set of your own calipers online for about $10, so it is cheap.  The margin for error is high depending on the expertise of the person measuring, the quality of the calipers, and the formula used.  Typically calipers underestimate body fat by 2-3% points.  Whatever formula you use, measure exactly the same spot each time for the best consistency between measurements.

2.  Bioelectrical Impedance – This is the method body fat scales use.  The faster that electricity flows through the body the more lean you are.  Fat does not transmit electricity as efficiently as muscle.  Your hydration level also greatly effects the reading as well.  The better hydrated you are the faster electricity will flow through your body.  Fasting % BF measurements in the morning are usually higher than later in the day because we typically are dehydrated after sleeping all night.  No skill is needed to use this method, but it is horribly inaccurate.  I have seen my % BF measurement vary 4-5 % points depending on the scale settings, time of day, hydration status, and if I have eaten recently.

3.  Hydrostatic Weighing – This is commonly referred to as underwater weighing.  The concept is that fat floats more than lean muscle tissue.  It is very accurate if done properly, but proper measurement does require expelling as much air from the lungs as possible and correcting for air content in the bowel.  It is less convenient and more expensive than the two previous methods.  Hydrostatic measurement is accurate within 1-3 % points

4.  DEXA (Dual-Energy X-ray Absorptiometry) – DEXA is the current gold standard.  It is the most accurate of the 4 techniques.  Limited access, price, and the use of X-ray are cons.  Price can vary from $50 to $150 per study.  At my clinic, Tyler Internal Medicine Associates in Tyler, TX, we charge $50.

Most people don’t need to worry about dropping their %Body Fat too low, but realize that not all fat is bad.  There is an essential amount that we must maintain.  Essential  fat is found in nerve sheaths, walls of organs, bone marrow and muscles and is essential to normal functioning. Women have a higher
percentage of essential fat as it is also found in the breasts, lining of the uterus, hips and thighs. American Council on Exercise (ACE)  reports that the percentage of essential fat should be around 8 – 12 % for women and 3 – 5 %for men (but these figures do vary according to the source).

So what’s the best way to follow your weight loss and fitness plan?  Should you shoot for an ideal weight? There really is no such thing as an ideal body weight.  Think more about body composition.  I follow 4 metrics.  I weigh myself  once a week fist thing in the morning.  I measure my waist circumference every other week.  I monitor my strength gains weekly by recording the details of my workouts.  Finally, I check % Body Fat every 4 months.

Pick a couple of metrics and follow them regularly.  Remember weight is only part of the story.

Here’s to the Journey!