The two types of fat in the body are essential fat and nonessential fat, or storage fat. Essential fat is needed for normal physiological and biological functioning. It is placed throughout the body from the internal organs to the brain and spine. The level of essential fat is approximately 3 % for men and 12% of total body weight for women. Women have gender specific deposits of fat and a drop below the essential can impair the bodily functions. Women generally have a higher percentage of body fat than men do, here are gender difference in where the fat is stored as well. Different body types are characterized by higher fat storages in different boy parts. For example the gynoid or pear shaped body type in women with more fat storage in the hips and thighs. Males and females have different receptors in different areas that are more or less responsive to mobilizing fat. the female hormone estrogen has several roles in resting and exercise fat metabolism. One of the methods that is used to determine the use of fat as fuel is the respiratory exchange rate. (RER) A lower RER is an indication of a greater at metabolism and a higher RER is an indication of a greater carbohydrate metabolism. There are gender differences in exercise metabolism during different exercise intensities. Without specific equipment to test, one can have an estimated level of intensity by determining their rate of perceived exertion and heart rate levels. The different fat distributions is determined by differences in hormones, hormone receptors and enzyme concentrations and other variables. A persons body type ( and fat deposition patterns) will also be a factor in predicting different health risks.
Non essential fat is storage fat or subcutaneous, below the skin fat. Storage fat that surrounds the organs is referred to as visceral fat. Age is also a factor as to where a persona will have more fat storage. Thus when doing your body composition testing the numbers of ideal body fat percentages will increase as you age. Nonessential fat has three main functions: an insulator to retain body heat, padding against trauma, and as an energy substrate during rest and exercise.
Fat Mass is the absolute amount of body fat, the relative fat is the amount of fat expressed as a percentage of total body weight. Body fat accumulates in two ways: increasing the size of existing fat cells and the formation of new fat cells. Fat in the body is in the form of triglycerides (TG) (three fatty acid molecules held together by a molecule of glycerol. During exercise, TG in fat cells, muscle cells and in the blood can be broken down (lipolysis) and used as fuel by the exercising muscles.
Fat mobilization refers to the process of releasing fat from storage sites. there are two main enzymes that regulate the mobilization of free fatty acids. The breakdown of fat, or oxidation of fat into energy that the body can use, occurs primarily in cardiac and skeletal muscle and the liver. A metabolic training effect of aerobic exercise is an enhanced ability to mobilize and break apart TG for energy use. Additionally it is possible to increase the response of the body to be activated by lower concentrations in a trained individual compared to a non-endurance trained individual.
What exercise burns the most fat?
During low -intensity exercise the majority of energy comes from fat. As the exercise level increases the percentage of energy derived from fat decreases. However, the absolute amount of energy increases. Therefore expressing energy derived from fat as a percentage without considering the total is misleading. When you are doing your cardio training on a machine you do not necessarily want to stay in the somewhat misleading fat burn zone. One must also consider the effect that the exercise will have on energy expenditure after the exercise session is completed. Your program should be individualized for fitness level, health, age, goals, risk factor profile, medications, behavioural characteristics, and individual preference. Strength and flexibility training will also have an impact on aerobic and cardiovascular training. There are some specific periodization suggestions from which to individualize the recommendations for optimizing fat during aerobic exercise.
Stanley P, Brown, Wayne C. Miller, Jane M, Eason, Exercise Physiology : Basis of Human Movement in Health and Disease
Regenesis Fitness 