How does Body Fat influence BMI

How does Body Fat influence BMIBehind the well known BMI (Body Mass Index) calculation lays much topic for discussion. Started as a general indicator of acceptable weight range, is the BMI calculation for many an A to Z. But the real value of the BMI calculation lays in something that should only be taken generally and not literally. One very good reason for this is that the weight of body fat is also included in the calculated result, this is why the BMI is of less value to athletes and highly trained people.

What about the fat?

Fat weighs volume for volume much less than muscle and at the same time takes up more space in relation to its weight. A trained or muscular person weighing 60 Kg is much slimmer than a fatty person at 60 Kg and here lays the problem.

The BMI for both the muscular person and the unfit fatty person will work out to the same result because the BMI calculation doesn’t take into account anything but the height and the weight. It is therefore possible to have a healthy BMI but still be carrying an unhealthy amount of fatty tissue. That a BMI calculation does also not consider bone size and density, is this especially true for people with quite low muscle mass and small skeletal frames, for example small boned, untrained women.

Think here about the difference in visual volume in 250 gram Butter compared to 250 gram Beef or Pork (or whatever else you like to eat ;)) While you’re at it, think about the texture too.

This is one reason when after starting on a fitness or training programme why your jeans are not pinching so much as before, but you still weigh the same. In effect you’re reducing fat whilst increasing muscle mass, sometimes you can even weigh a little more and still measure centimetres slimmer.

How can we get a better result?

With a BMI calculation alone it’s simply not possible to get a better result. You can only rely on your own judgment, or that of other people, friends or professionals. This is why, although the BMI remains a useful indicator, it’s a good idea to use it together with other calculations such as waist to height (WHtR) or a Body Fat / Lean Body Mass calculation. Or by using it together in combination with the old fashioned way with callipers that measure surface fat thickness on various parts of the body, ask at your gym - they’re sure to know about these.

A good compromise

Remember: the fat that you can see on the outside of your body isn’t the only fat that our bodies contain, the inner organs are also protected by a layer of fat to provide padding and to assist in important bodily functions, but more or less fat than required is unhealthy. A good compromise is to combine waist to height and BMI together, taking both measurements and calculations you can get an acceptable indicator if your body has too much, or too little, fat content. The BMI calculation can give you a very general direction, the waist to height (WHtR) calculating if your waist measurement is within the correct range and proportion for your height. Even better if you count your ideal weight for your height and age also in.