FAT

Food Science
Along with proteins and carbohydrates, one of the three nutrients used as energy sources by the body. The energy produced by fats is 9 calories per gram.

Proteins and carbohydrates each provide 4 calories per gram.
Total fat ;the sum of saturated, monounsaturated and polyunsaturated fats. 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.

Fats are the major component of the flabby material of a body, commonly known as blubber.
Body fat measurements and the measuring tape are recognized as superior methods for measuring "weight loss". When one declares that they want to "lose weight", what they often mean is that they want to lose fat.

First, body fat percentage is simply the percentage of fat body contains. If 150 pounds and 10% fat, it means that body consists of 15 pounds fat and 135 pounds lean body mass (bone, muscle, organ tissue, blood and everything else).

A certain amount of fat is essential to bodily functions. Fat regulates body temperature, cushions and insulates organs and tissues and is the main form of the body's energy storage.

Knowing your body fat percentage can also help determine if weight loss goals are realistic. Weight loss doesn't always mean fat loss.

For example:
Let's say 130lb woman with 23% body fat, and the goal is to "lose 20 pounds":
Initial body fat: 130lb x 0.23 fat = 30lb body fat
Lean body mass: 130lb total – 30lb fat = 100kg lean body mass (bones, organs and all else)
Goal: 130lb – 20lb = 110 pounds

As you can see, the goal of losing 20 pounds is not realistic or healthy. At 110 pounds, this woman still requires 100lb of lean body mass (bones, organs, etc.), but would only be carrying 10lb, or only 9% body fat. From the chart above, can see that this is a dangerously low percentage.

A better goal might be for the woman to reduce her body fat from 23% to 18%. In this case:
130lb x 0.18 = 23 lb body fat
100lb lean body mass + 23 lb = 123lb goal weight

So, for this individual to achieve a lean, but healthy 18% fat, she would need to lose only 7 pounds of fat, reducing her weight from her current 130 pounds to 123 pounds. Losing more than 7 pounds means losing lean body mass (usually metabolically-active muscle tissue), which is clearly not desirable.

So before you decide that you need to "lose weight", remember to consider that "weight" consists of both lean body mass and body fat. Try to keep your weight loss goals realistic, and remember, keep the calorie-burning muscle, and lose only the fat.
Food Science