ABSTRACT
Lipids play a key role in the body both as stores of energy and as cellular signals for a number of essential physiological processes. Dietary fats and the fats stored in the body are predominantly triglycerides consisting of a three-carbon backbone (glycerol) and three fatty acids linked to these carbons. In the process of digestion, the fatty acids are removed from the backbone and then reattached in the cells of the body. This complex process enables the body to modulate the biology of the fats ingested to avoid starvation and infection, the two major threats to the survival of ancient mankind. From an evolutionary standpoint, lipids represent the most effective store of portable energy, carrying 9 Cal/g, but the cells adapted to store this lipid evolved in an environment where storage of energy was critical to survival. There was no evolutionary pressure for ridding the body of excess dietary fat and calories. The modern environment, where the increased availability of foods and a sedentary lifestyle have led to the common occurrence of positive calorie balance, is a relatively recent development in human evolution. It is now recognized that this positive energy balance has led to an activation of innate immune responses evolved in ancient times to protect the body from infection. However, when persistent activation of inammation occurs even at a low level, as it does in visceral obesity, it is associated with the many diseases affected by excess inammation that are associated with obesity and discussed elsewhere in this text.
