The first part of this second chapter focuses on experimental techniques for collecting gut tissue from human subjects for testing cellular pathway activity in obesity. Clearly identifying the precise region of the stomach being tested for cellular responsiveness to dietary fat is fundamental because the human stomach has different areas identified in laboratory tests based on regional expression of genes linked to food intake. Cell-type specific gene expression was first reported in a series of experiments on human colons to study the effect of high fat diets on fat oxidation and fat storage. This approach has been extended and applied successfully to fat absorption and fat metabolism.

In recent years, the focus has been on fat absorption and the role of fatty acids in regulating appetites. Most dietary fat is oxidized by the liver first before it is absorbed into the bloodstream. The second step involves transport of the oxidized fat to the cell membrane where it undergoes a complex series of reactions which include the regulation of multiple biochemical steps. Several biochemical processes are involved including fatty acid oxidation and the production of long chains of fatty acids.

Several recent studies have focused on the role of fatty acids in energy metabolism. They showed that fatty acids can increase the burn of calories and reduce the absorption of fat during fasting. The study also showed that the increase in fatty acids is affected by insulin. Insulin resistance and glucose resistance are likely to be affected by fatty acids and specifically by the ability of the cellular machinery to produce and secrete insulin. The insulin that is produced by the insulinoma cell machinery does not actually act directly on the fatty acyl-CoA molecules in the body; however, the process is similar to how glucose is metabolized in the body. Therefore, the fatty acyl-CoA molecules are transported to the cell membrane and metabolic pathways are initiated.

Acetyl-CoA has recently been shown to regulate fatty acid synthesis and metabolism in muscle tissue. Muscle homeostasis depends on the ability of the cells to absorb nutrition and use it for energy. When there is a deficit of fatty acids, the ability of these muscles to respond to demand for energy is reduced and the results are fatigue. Exercise training is a necessary part of maintaining good health. Fatty acids help to improve endurance and strength development.

One of the most exciting benefits of using dietary supplements with natural extracts is that they help to control the amount of glucose that is used by the cell membranes to absorb fatty acids. These extracts appear to promote better cell membrane health in aging animals as well as in healthy humans. The researchers showed that, unlike the conventional drugs that inhibit fatty acid metabolism, the new fat-absorbing supplements reversed obesity. This is probably because the free fatty acids prevent the entry of glucose into the body and the accumulation of excess fat deposits.

Another benefit of these supplements is that they help to reduce the damage to the cell membranes that occurs during fatty acid synthesis. Normally, this process is initiated by insulin and it is believed that fatty acids can prevent insulin release by limiting its uptake by the cell membranes. The new supplements prevent insulin from binding with fatty acids that are taken up into the cell. They also prevent glycosylation, a process by which sugar accumulates in the fat droplets. Obesity is clearly caused, at least in part, by excess sugar in the fat droplets, and the supplements may help to correct this problem.