Fat cells are distributed all around the body and are not necessarily inert from a metabolism standpoint.
Fat storage is defined in to the following categories:
Essential Body Fat
This serves as a protection for organs, the immunity and inflammatory responses, the structure of hormones, insulation for nerves and the brain. This totals around 3% of body weight and is necessary for life.
Brown Adipose Tissue
The main role of this is to provide heat. The amount of this found on the body is thought to be related to genetics. It is currently unclear how this type of fat relates to fat loss or gain though through thermoregulation it directly relates to how many calories we burn through the day.
White Adipose Tissue
This is the primary type of body fat storage. These fat cells are composed of between 80% and 95% of lipid with the rest composing of water. They are made up of a molecule of glycerol bound to three fatty acids. Fat is a stored energy source and 1 pound of fat contains 3,500 calori0es (1 gram of fat contains 9 calories). In contrast the body at its maximum contains 500 grams or around 2000 calories of glycogen (which will not necessarily meet daily energy requirements). This is the target for those looking to improve their physiques.
The classification of body fat also depends upon its deposition site:
Sometimes referred to as internal fat, this type of fat is found around your organs. Typically, this is found around the torso and if found in abundance is termed central obesity. As well as the obvious cardiovascular health risks of central obesity this has also been linked to insulin resistance. This type of fat is mobilized as energy, has a better blood flow and is less effected by elevated insulin levels as it will not always stop releasing fatty acids during periods of high insulin (considered a problem from a health perspective). This appears to be mobilized more readily by aerobic exercise which will be discussed later. Typically this is packed around the organs. Individuals with high levels of internal body fat will not necessarily present as “fat.” It highlights though that thin does not necessarily mean healthy.
This type of fat exists under the skin and is the main emphasis of most fat loss programmes as it is the most prominent incorporating between 40 to 60% of your body fat.
In the next post I will discuss the disrabution of body fat and sex differences.