Monday, 06 July 2009

• How Do I Know What a Healthy Weight is For Me?

  
  

   What exactly is a healthy weight? Due to increased media influence and other factors, it can be difficult to judge what your body should look like. We see models everywhere that appear thin and fit. Are their weights what we should be aiming for? In reality, many models are not at a medically healthy weight - instead they are underweight, and being underweight can cause just as many medical problems as being overweight. If we shouldn't be looking to fashion models for health, then where should we look? It's back to the textbooks and research for this one as we explore some different methods of determining what a healthy weight really is.

  Weight to Height Ratios

  Body Mass Index

  When determining a healthy weight, one can use a variety of methods - the most popular being Body Mass Index (BMI). Your BMI is calculated from your weight and your height. It does not directly determine your percentage of body fat, but through research it has been determined that it is reliable for most individuals. If you are a serious athlete, it may not be as accurate due to increased percentage of muscle mass.

  BMI	category
  <18.5	underweight
  18.5-25	healthy
  25-30	overweight
  30-35	obese
  35-40	significantly obese
  40-45	morbidly obese
  45-50	super obese
  >50	super-morbidly obese

  The metric system calculation is simple:
  

  weight(kg) / height(m)²

  or you can use this modified formula for the English system:

  ( weight(lb) / height(in)² ) * 703

  For instance, if someone was 5'5" (65 in, 1.65 m) and 130 lbs (59 kg) they would have a BMI of 21.67, thus putting them in the healthy weight range for their height.
  
  You can also use this handy chart:
  

  
  

  An interesting website allows you to see what people would describe as their ideal weight based on your height along with your BMI and several other formulas.

  Body Fat Percentage
  

  Another category of determining healthy weight is through body fat percentage. This allows you to determine what amount of weight on your body is due to fat-free mass (vital organs, muscle, skin, etc.) and what amount of weight is due to fat. There are several ways to do this including the use of a body fat formula, calipers, bioelectrical impedance, and hydrostatic weighing.
  

  	women		men
  essential fat	10-12%		2-4%
  lean/athletes	14-20%		6-13%
  ideal	21-24%		14-17%
  average	25-31%		18-25%
  overfat	32%+		25%+

  
  

  Calculating your ideal weight from your percent body fat
  

  Again, take a look at the 5'5" (165 cm), 130 lb (59 kg)  person. Let's say that she has used one of the following methods to calculate her percent body fat and has found it to be 30%. The highest ideal body fat percentage she should have is 24%, so she needs to lose 6% of her body fat. Multiply her current weight, 130 lbs, by .06 to find the amount of fat she should lose. 130 * .06 = 7.8 lbs. Subtract this from her current weight to find her ideal weight: 130 - 7.8 = 122.2 lbs. Ideally, she should weigh 122.2 lbs (55.4 kg).
  

  Body Fat Formula
  There are actually several formulas that can be used to estimate percentage body fat.
  
  Formula 1:

  Body Fat % = (1.20 x BMI) + (0.23 x Age) - (10.8 x gender) - 5.4

  (male gender= 1, female=0)

  Formula 2:

  Body Fat Formula For Women
  Factor 1	(Total body weight x 0.732) + 8.987
  Factor 2	Wrist measurement (at fullest point) / 3.140
  Factor 3	Waist measurement (at naval) x 0.157
  Factor 4	Hip measurement (at fullest point) x 0.249
  Factor 5	Forearm measurement (at fullest point) x 0.434
  Lean Body Mass	Factor 1 + Factor 2 - Factor 3 - Factor 4 + Factor 5
  Body Fat Weight	Total bodyweight - Lean Body Mass
  Body Fat Percentage	(Body Fat Weight x 100) / total bodyweight
  Body Fat Formula For Men
  Factor 1	(Total body weight x 1.082) + 94.42
  Factor 2	Waist measurement x 4.15
  Lean Body Mass	Factor 1 - Factor 2
  Body Fat Weight	Total bodyweight - Lean Body Mass
  Body Fat Percentage	(Body Fat Weight x 100) / total bodyweight

  Or you can use this handy calculator.
  

  Skin-fold Measurement

  
  

  
  

  Another way to measure body fat percentage is through the use of calipers. Calipers are tools that measure skin-folds on certain areas of the body. The theory behind calipers is that half of a person's fat lies just below the skin. It is best to have this done by a professional, as it is difficult to get accurate measurements unless you are experienced. However, you can do this at home. Calipers can be purchased off of many different fitness websites or at your local sporting goods store.

  
  

  Hydrostatic Weighing
  

  Hydrostatic weighing is more commonly known by lay persons as underwater weighing because, well, you're literally weighed underwater. This method of measuring body fat is considered to be the most accurate; it is also the most difficult to do at home. However, if you can find a facility near you that is set up for it (such as a some fitness gyms, universities, or research facilities), it's quite easy to do. First your dry weight is determined, then you are weighed under water. These weights are used to calculate your body density, which can then be used to calculate your percent body fat using the Siri equation.

  Body Density = Wa / (((Wa - Ww) / Dw) - (RV + 100cc))

  Wa = weight (kg) in air
  Ww = weight (kg) in water
  Dw = density of water
  RV = residual volume of air in lungs

  Bioelectrical Impedance Analysis (BIA)

  
  

  You know those silver plates that you see on certain bathroom scales? Well, they measure your percent body fat based on bioelectrical impedance. BIA is based on the idea that fat-free tissues, where the majority of body water is located, are better conductors of electricity than fat. To do this, a small electrical current is sent through the body and the resistance is measured. The amount of electrical resistance is then correlated with the amount of fat-free tissue and, taking into consideration your weight and height, this is used to calculate your percent body fat.
  

   Body Frame, Weight, and Height

  
  

  Another method to determine a healthy weight (which is considered more accurate than BMI yet less accurate than body fat percentage) is by comparing your weight, height, and body frame. Although no person is exactly alike in body structure, body frames are measured in three different sizes: small, medium, and large.

  The easiest way to figure out what type of frame you have is by wrapping your thumb and pointer finger around your opposite wrist between the bony part and your hand. If your fingers overlap you have a small frame. If they barely touch you have a medium frame. If they don't touch you have a large frame. For a more accurate way to determine your body frame size, you can go to this website.

  To figure out your ideal weight based on your height and frame size, you can use an online calculator (click here or here).

  So that's about it!

  Have you used any method to determine how much you should ideally weigh? Are you at a healthy weight for your height?

  
  

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