Actual Body Fat

A MORE DETAILED EXPLANATION OF WHAT BODY FAT IS AND DOES.

The fat in the body serves several purposes.  Firstly, it cushions some of the internal organs such as the kidneys, secondly, the fat that is mostly situated under the skin serves as a store of energy, (which is the fat we call on as we lose weight) thirdly, this subcutaneous fat determines to a large extent body contours and hence sexual attraction, (the fat we don't want to lose) and fourthly, it acts as an insulator and so conserves body heat. (Which is why we feel the cold a little more when we lose weight)

The fat is present inside living cells, which constitute the adipose tissue(this is just another name for fat).  this is a metabolically active organ.  After a meal, the glucose and fatty acids arising from the food enter these cells and are built up into fat.  When no food is taken and energy is required, the fat is broken down into fatty acids and released into the blood for oxidation, this is losing weight!  both synthesis of fat and its breakdown are under the control of hormones, mostly insulin and adrenalin.

The fat that is stored in the adipose tissue tends to be characteristic of the species in whose body it is found, pork fat different from beef fat.  However, a diet rich in fat may influence the nature of what is stored.  The fat in a person who habitually takes a high proportion of dietary fat as vegetable oils, for example, will tend to be rather softer than that of a person whose dietary fat is largely the solid fats of animal origin.  So we really are what we eat - including softer or harder!!

It follows from this that the fat does not exist simply as if it were a inert piece of lard or dripping.  It is present inside living cells that are continually metabolizing, that is, carrying out innumerable complex reactions common to all the cells of the body as well as the special reactions involved in the storage and release of the fat.  It is important to bear all this in mind when considering some of the ways popularly believed to be effective in the treatments of obesity.

The total fat in the normal individual amounts to about 12% of the body's weight in men, and about 25% in women.  A substantially greater proportion than this is considered to denote obesity, a substantially lower proportion indicates a degree of starvation or the existence of some wasting disease, where it can be as low as 1kg.  A rough assessment of the amount of fat is given by the weight of the body, but this can be deceptive if an unusually higher weight than expected is due the well-developed musculature of an athlete.  Does this apply to anyone here?

Because much of the surplus store of fat is found just beneath the skin, an assessment of this can be used to estimate the total amount of fat in the body somewhat more accurately than be weighing the body.  It can be done by measuring the thickness of a skin-fold, by doing this at three or four sites on the body, one can get a value that can be judged against standards used by research workers who have calibrated skin-fold thickness against the percentage of body fat.  For the same skin-fold thickness, there is rather more fat in the body in older people than in younger.  In addition, the same skin-fold thickness indicates more fat in women than in men.  This is why we 'pinch an inch' to decide on the degree of fatness - rather inaccurate though.

There are two other methods that can be used to measure body fat, but they are elaborate and time-consuming, more suited for research than as a routine.

One such method depends on the fact that the density (specific gravity) of fat is less than that of the rest of the body.  Fat weighs rather less than does the same volume of water and the rest of the body weighs rather more than water.  The values for specific gravity are, roughly 0.90 for fat and 1.10 for the fat free body.  By weighing a person in the ordinary way, that is, in air, and then when he is totally immersed in water, the density of the whole body can readily be determined.  From this, the proportion of at can be calculated, for example, if the density of the body is 1.05 then the proportion of fat can be calculated to be 21% from the formula % Fat = 495/density - 450  This is only for the more technically minded amongst you.

Probably the most accurate way of determining body fat is also the most expensive.  It depends on measuring the radioactivity of the body which is a measure of the amount of potassium in the body.  Since the potassium is almost entirely in the body's cells, the 'cell mass' can be calculated, the smaller this is in relation to the total weight (mass) of the body, the more fat the body contains.  This is because the fat itself, inside the adipose tissue cells in which the fat is stored, contains no cellular material.  This method is rarely used because it requires a very expensive piece of equipment called a whole body counter.