Classification and function of adipose tissue

Adipose tissue is a loose connective tissue composed mostly of adipocytes. Adipose tissue has traditionally been classified into white and brown type adipose tissue, although a third type of inducible brownlike adipose tissue or “beige” has emerged.

White adipose tissue stores energy, for example, in the form of triglycerides, whereas brown and beige adipocytes consume energy.

Fat storage is a specialized function of adipose tissue and it represents the major fuel depot of the body; it is as essential to normal function as any other tissue. This function is performed by adipocytes, which comprise the vast majority of cells in adipose tissue.

Body fat serves other important functions: It insulates the body against low environmental temperatures and serves as a shock absorber.

In many mammals, including human infants, brown adipose tissue is also presents for thermogenic function in the absence of shivering.

Typically, fat stored in adipose tissue represents 15 percent to 20 percent of men’s weight and 20 percent to 25 percent of women’s average weight.

During obesity, there is a marked expansion of white adipose tissue, especially in the visceral compartment, along with profound disruption of resident leukocyte homeostasis prompting chronic inflation and metabolic dysfunction.
Classification and function of adipose tissue

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

Saturated fat in food

Saturated fats mainly found in animal foods – meats, whole milk, and cheese. Some vegetable fats such as coconut and palm and hydrogenated fats provide smaller amounts of saturated fats.

Coconut oil contains as much as 92 percent saturated fats – more that any other oil, including beef fat and lard.

In the 1950s and 1960s when saturated fats was first being associated with elevated cholesterol, researchers began looking for other effects caused by saturated fat.

High intakes of saturated fats contribute most of high blood low density lipoprotein LDL cholesterol. It contributed to heart disease, obesity and other health problems.

Most notable among the saturated fatty acids that raise blood cholesterol are lauric, myristic and palmitic acids.

A fatty acid molecule that has two hydrogen atoms attacked to each carbon is said to be ‘saturated’ with hydrogen because it is holding all the hydrogen atoms it possibly can. This fatty acid is called a saturated fat. 

Generally foods that high in saturated fats content are solid at room temperature.
Saturated fat in food

Monounsaturated fatty acids

Monounsaturated fatty acids are a fatty acid containing one point of unsaturation.

Plant sources that are rich in monounsaturated fatty acids include vegetables oils that are liquid at room temperature (eg, canola oil, olive oil, high oleic safflower and sunflower oil) and nuts.

When monounsaturated fat such as olive replaces started and trans fats in the diet, the risk of heart disease may be lessened.

Monounsaturated fat as in seafood, nuts, olive oil, canola and coconut oil, are considered the healthiest fats.

They are rich with fatty acids and important for normalizing prostaglandin levels. Studies suggest that deist rich in monounsaturated fats might be of benefits, especially for diabetes with insulin resistant.

A diet higher in monounsaturated fatty acid appeared to provide an advantage over a fiber-rich, high carbohydrates, low-fat diet on body fat distribution among diabetics.
Monounsaturated fatty acids

Dietary Fat

Fat is the name given to a broad category of substances we get from our food or make in our bodies.

Fat is an essential nutrient, which contributes approximately 30-45% of food energy in western diets.

In technical they are referred to as lipids.

Fat along with proteins and carbohydrates, one of the three nutrients are used as energy sources by the body.

Energy is one of the principal nutritional requirements of man and fat is a principal source of the energy.

Each grams of fat consumed supplies the body with 9 calories worth of energy.

Total fat: the sum of saturated, monounsaturated and polyunsaturated fats. Cholesterol is from another lipid family called sterols.

Intake of monounsaturated and polyunsaturated fats can help reduce blood cholesterol when substituted for saturated fats in the diet.

In chemistry, a compound formed from chemicals called fatty acids. These fats are greasy, solid materials found in animal tissues and in some plants.

For most part, human di not require fat sources in their diets because the body can synthesize most of the fatty acids it needs from other constituents, including carbohydrate and protein.

The brain needs saturated fats, polyunsaturated fat, cholesterol, and a number of other fats.

Fats are also a component of cell membranes, vitamin D and sex hormones.

Some types of fats give cell membranes flexibility and help regulate the transfer of nutrients into and out of cells.

While others serve as precursors to vitamin D and sex hormones, such as estrogen and testosterone.

Most saturated fats come from animal products. Unsaturated fats are prominent in both animal and vegetable foods.

The importance of dietary fat is underscored by the fat that 35% of the weight gain of an infant in early is accounted for by fat.

Most of the dietary fat is in the form of triglyceride formed by the three fatty acids esterified to a glycerol backbone.

The role of fat in the diet is both physiological and psychological. In its psychological aspect, it is important to appearance and taste of foods.
Dietary Fat

Summary of Fats

Summary of Fats
Fats are comprised of fatty acids bound, in bundles of three, to glycerol.

• Fatty acids are either saturated, monounsaturated or polyunsaturated.
• Fats contains mixtures of all three types of fatty acids; the balance of the mix determines whether the fat is generally saturated (hard) or polyunsaturated (soft).
• Fats are insoluble in water and require special treatment for digestion and transport.
• In digestion, bile acids act as detergents to solubilize fats to aids digestion.
• In transport, the fatty material is surrounded by a coat of protein plus phospholipid. The full particle is a lipoprotein.
• The liver can convert carbohydrate to fat, which is exported from the liver as a lipoprotein.
• Certain polyunsaturated fatty acids are nutritionally essentially because:
  1. They are the precursors of the vitality important regulators of metabolism, the prostaglandins
  2. The body cannot make them from either carbohydrate or existing dietary fatty acids.

Summary of Fats

Age Changes in Body Composition

Age Changes in Body Composition
Even though the water content of the lean body mass in adults is very constant at 75% that of newborn infants and fetuses is somewhat greater. Indeed there is a “drying out” of the body age, as well as change in the intra and extra cellular distribution of water.

The overall fat concentration of the body increases during gestation until birth, and the water content declines from birth to adulthood. If the infant is premature, there is an additional loss of water with age related to the change in fat content. Although the water content declines, the nitrogen content increases, reflecting a higher protein concentration in adult tissues as compared with that of the newborn infant or fetus. The changes from a greater to a lesser extracellular fluid volume with growth and development are reflected in the decreased sodium concentration of body tissue with age and increase in potassium concentrations. The overall contributions of calcium, magnesium and phosphorus, most of which are present in the bone, also increase dramatically from birth to adulthood, coinciding with the process of body “mineralization”.

While the proportion of the body water in the central nervous system, skin and subcutaneous tissue decline that most other organs increase, especially in the muscles. Perhaps more of the organ systems including muscle and parenchymal tissues, increase their proportion of intracellular water, where as the opposite is true of the skin and subcutaneous tissue.

These trends continue during aging. Western adult slowly losses lean body mass and accumulates more fat onward from early adulthood. The loss of lean body mass is more evident in men than women until after menopause, when it accelerates. This change is ascribable mainly to loss of cellular versus extracellular mass, reflected in losses of potassium and nitrogen that average 22.5% and 17.5%, respectively from 25 to 75 (for both sexes).
Age Changes in Body Composition