Fat storage is more complex than portrayed by the medical establishment. Fat stored in the abdominal compartment is associated with an increased risk of mortality. This fat is not visible, and is often present in normal weight individuals. Deep abdominal fat, sometimes called visceral fat is associated with disease because it is thought to signify the presence of metabolic syndrome, a condition characterised by metabolic dysfunction. However, in addition to the viscera, triglycerides can be stored in the subcutaneous compartment. This fat is not associated with an increased mortality and is visible to the exterior, often being particularly conspicuous in the buttocks, abdomen and thighs. The fat distribution of subcutaneous fat is known to vary between male and female subjects. It is thought that gender variations in subcutaneous fat distribution are the result of hormonal differences, with oestrogen causing more buttock and thigh fat.
Different areas of subcutaneous fat can also contain different ratios of fatty acids. For example, one group of researchers1 investigated the fatty acid compositions of the abdominal and buttock subcutaneous regions in 143 autopsied adult humans aged 24 to 61 years. Overall, the most common type of fatty acid in both subcutaneous compartments was monounsaturated. Saturated fatty acids made up the next most common type of fatty acids, followed by polyunsaturated fatty acids. Polyunsaturated fatty acid composition was similar between the two subcutaneous compartments, but abdominal subcutaneous fat contained more saturated fatty acids, whereas the buttock subcutaneous fat contained more monounsaturated fatty acids. In addition the researchers measured a deeper perirenal site, not considered a subcutaneous compartment, and found differences again. Here saturated fatty acids were more common, and monounsaturated fatty acids less common, when compared to both subcutaneous sites.
Therefore differences in the preference for fatty acid storage may exist in humans. These results show that subcutaneous abdominal fat is more saturated than subcutaneous buttock fat. This may suggest that the metabolic activity of the tissues differs such that deposition and mobilisation rates are affected, thus reflecting the differing requirements for fat in particular areas with respect to the different functions it may serve. For example, it has been suggested that fat deposits in particular regions of the body may serve a particular function in that region, such as protection. This may change the requirements for fatty acid storage. Interestingly the authors noted that the concentration of the essential fatty acids linoleic acid (LA, C18:2 (n-6) and α-linolenic acid (ALA, C18:3 (n-3) were similar in all three compartments, suggesting that sampling of adipose tissue to assess dietary intake of essential fatty acids might be possible from any fat region.
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