Human body fat

Fat is a normal component of the human body that is stored in adipose tissue. The only body measurement that directly calculates the relative composition of the body and present a measure of fitness level, regardless of height and weight, is body fat percentage (% BF). Widespread application of Body Mass Index (BMI) affords a measure which enables comparison with the overweight of individuals of different heights and weights.

Fat and fat-free mass have very different energy densities:
• Fat: 39.4 MJ/kg
• Fat-free mass: 3.7 MJ/kg

All fat is not bad. Fat is very important for cells, it keeps the body warm, and it also cushions the body and provides comfort, such as when the body sitting. However, too much fat can be a risk factor for obesity. An ideal body composition is one with healthy amounts of fat mass and lean mass, or muscle. The average body fat of a healthy person is about 10 percent to 15 percent for men and 15 percent to 25 percent for women.

Why body fat is so important?
*Fat is an insulator; it helps the body to adapt to heat and cold.
*Fat acts as a shock absorber; it can help protect the body organs and bones from injury.
*Fat helps body use vitamins effectively.
*Fat is stored energy that is available when human body needs it.
*Fat, in reasonable amounts, helps to look the best, thus increasing the feelings of well-being.

Accurate determination of body fat could provide clinically useful guidance for physicians to assess disease risks in patients with obesity and optimize preventive or therapeutic remedies for these patients.
Human body fat

Fat distribution in human body

The term fat distribution refers to the relative amounts of fat in the primary compartments where dispose tissue and fat are stored in the body.

Fat is present, in a higher or lesser degree in almost every anatomical compartment, inside parenchymatous organs, muscle and breasts and it is stored mainly in the omentum (intra-abdominal fat); this is the so-called ‘central’ fat and it is the most involved in metabolism variations, increasing in obesity and reducing in the case of weight loss.

There are some anatomical districts where adipose fat are present and these structures devoted to produce more protection in the regions of attrition: around kidneys, inside joint, underneath the breasts, deep in face, inside the hand, and over the os pubis. This fat almost no influence on body silhouette and a few on face traits.

In terms of fat percentage, males reach peak values during early adolescence and then show a decrease throughout adolescent growth, probably due to a rapid accumulation in lean body mass, whereas females, after an initial decline, show a continuous increase in fat percentage throughout their eighteenth year.

With aging, body fat in men slowly increases from 18% in those 18 to 25 years of age to 36% in those 65 to 85 years old; in women, a gradual increase from 33% to 45% is found in similar age groups.

Distribution of body fat is important in evaluating the risk of disease. Excess body fat around the abdomen is associated with higher disease risk than is excess fat around hips and thighs.
Fat distribution in human body

Fat cells and adipose tissue

Fat cells are normally present in loose connective tissue either singly or in small groups. Fat cells are created from stem cells in fatty tissue that develop into mature, long-lived fat cells that signal immature fat cells to divide and reproduce as needed throughout life to store excess calories as fat and to disappear when no longer needed. When large numbers of these cells are organized, the resulting lobules constitute adipose tissue.

Adipose tissue is sometimes referred to simply as fat. Adipose tissue may be partitioned by connective tissue septa into lobules. While in the subsequent developmental phases the lobules continuously increase in size.

The special capability of fat cells is the storage of a fuel reserve, which may vary in extent from an approximate 40-day reserve in the average person to one sufficient for a year or more in some obese individuals.

Brown adipose tissue

At first, fat cells were thought to be placid repositories of excess fuel which, when organized into subcutaneous layers, served as insulting material to prevent loss of body heat.

When the individual is on reducing diet, adipose tissue undergoes a process called lipolysis. Lipolysis is the separation of fatty acids from the stored form of fat, and release of the fatty acids into the blood so that they can be used by tissues and organs as a source of energy.

Another recognized function of adipose tissue was it ability to cushion, support abdominal organs and shapes the body.
Fat cells and adipose tissue

Body fat composition

Total body fat consists of essential fat and storage fat. Essential fat is important component for normal physiological function.

Essential fat constitutes about 3 percent of the total weight in men and 12 percent in women.

While storage fat represent for the energy reserve, it is fond mostly beneath the skin and around major organs.

Body fat levels differ significantly among men and women, contributing factors include genetic predisposition, physical activity patterns, and nutritional status.

Average values of percentage body fat approximate 15% for young men and 25% for young women. 

Normal physiologic function in women requires a certain level of body fat stored in the breast hips and thighs.

The fat component of the body usually is called fat mass or percent body fat. The non fat component of the body is termed lean body mass.

In contact sports and activities that require muscular power such as football, sprint, swimming and running, successful performance typically requires a large fat free body mass with average or blow average body fat.
Body fat composition

Fat is a reserve form of fuel

The lipids in foods and in the human body, though many in number and diverse in function, generally fall I three classes: triglycerides, phospholipids, sterols.

When the people speak off at, they are usually talking about triglycerides. Most animal fats are saturated and hence, solidify at low temperatures.

Most vegetables oils are unsaturated and, hence remain fluid.

Oxidative breakdown of fats yields more than double the amount of energy yielded by glucose, because of their poor oxygen contents.

These can be stored in an almost pure unhydrated form in large amounts in lesser space. Fat is stored with a very minimal amount of water, so fat stores are more compact and thus store significantly great amounts of energy than carbohydrate reserves.

Hence, fats serve as the best storage of spare energy in the form of ‘reserve stored food’. Gram for gram, fats provide more than twice the energy of carbohydrate or protein, making fat the most efficient storage form of energy.

The body fat found on a normal-weight person contains more than enough energy to fuel an entire marathon run or to battle disease should the person become ill and stop eating for a while.

For the typical 125 pound woman, roughly 20 percent of body weight – about twenty five pounds – is fat. 

Statistically, most of people carry more than that. Excessive fuel storage over the long haul taxes the body, precipitates disease and shortens life.
Fat is a reserve form of fuel