by
Dr. John M. McDonough
www.theweightlossresource.com
Summary
For any weight program, the most important hormones to remember are leptin and ghrelin. Ghrelin tells you when you are hungry, and leptin tells you when you are full.
There are very many different hormones produced in our bodies. Each of them has its own job to do. The primary function of a hormone is to act as a messenger. It is released somewhere in the body, and sent to another place, where it instructs the receptor involved what has to be done. Since its role is essentially that of a messenger, the quantity of a hormone is usually quite small.
Here we will focus primarily on just a few hormones that can have a profound effect on hunger, weight and sleep, all of which are of interest to any weight management program. These would be:
There are many other hormones that you have probably heard of, such as epinephrine (adrenaline), cortisol, testosterone, estrogen, progesterone, prostaglandins in general, plus many others. This is a potentially very large field of discussion, far beyond the level of this page, so we will stick to those hormones mentioned above, that are involved primarily with weight/hunger/satiety.
The next four species of hormones are currently under intensive investigation, so information may change as more is learned about them. I only mention them here because it shows just how much research is going on in the field of weight management by serious scientists.
The orexin/hypocretins group is currently a very hot topic of research, so it is still in the early stages of development. As of now (2007), however, it is believed to be involved in evoking hunger and in addition, is related to sleep and narcolepsy. This work is so cutting-edge that even the names for the species are tenuous at the moment.
Obestatin is genetically related to ghrelin, but it evokes the opposite response, that is, it reduces the appetite, whereas ghrelin raises it. It is also a recent addition to the group (2005).
Nesfatin - 1 is another hormone (discovered in 2006) that contributes to the sense of fullness, or satiety. The work on this material is also very recent, hence incomplete.
Now, as far as hunger and satiety are concerned, the two main hormones we will focus on will be leptin and ghrelin.
Leptin (discovered in 1994) is produced primarily by our fatty tissue. Its production is called for by our insulin. Our insulin, in turn, was called for by the glucose produced by the food or drink that we consumed. The process is a little reminiscent of an old song from my youth: From the vine came the grape, from the grape came the wine, from the wine came a dream to a lover ... In this case, we have: from the food came the glucose, from the glucose came the insulin, from the insulin came the leptin, from the leptin came satiety. That's the way it's supposed to work, and it usually does. In addition, leptin can increase our metabolic rate.
Unfortunately, there are things that can mess up that beautiful song. One is a lack of sleep (please see Sleep and Weight). Another is high fructose corn syrup (please see my report on High Fructose Corn Syrup).
Ghrelin (discovered in 1999) is produced in the stomach. It is the hormone that makes us feel hungry. When we take in food, the glucose produced is supposed to suppress the production of ghrelin, thereby reducing our hunger.
The levels of both leptin and ghrelin both operate on a circadian rhythm. During the night, the level of ghrelin increases, getting us ready for breakfast. In addition, the level of leptin decreases, due in part at least, to melatonin. This also prepares us for breakfast. Do not disappoint your body. Eat breakfast!
Your natural production of melatonin is very important for many reasons, including sleep and weight control. The production of melatonin is favored by darkness. It is produced while we are sleeping, and peaks during the middle of the night. Light inhibits its production, so sleep in the dark, with no TV. Use nightlights when necessary.
The story of the discovery and development of insulin is a fascinating one, but too long to go into here. It is manufactured in the pancreas. As is widely known, insulin is the hormone that directs the cells to take up the glucose from the bloodstream. The insulin receptors are normally on the surface of the cell. They assist the cells to take up the glucose. When the cells have taken up all the glucose they can handle, the insulin receptors bury themselves inside the cell, away from the glucose in the bloodstream. The excess glucose is then converted to fat. The insulin also assists in the conversion of glucose to glycogen, for intermediate-term energy storage. (Fat is the long-term energy storage.)
Glucagon, like insulin, is produced in the pancreas. When the glucose level falls too low, glucagon is released into the bloodstream. This then goes to the liver, where it causes the liver to convert its glycogen stores to glucose.
Strictly speaking, thyroxine is not itself a hormone, but rather it is a prohormone. Nevertheless, it is involved in controlling the metabolic rate.
The above description has been greatly simplified in order to preserve the sanity of both the reader and the writer. But I think it is basically correct.
The author of this article is Dr. John M. McDonough, who frequently writes on topics involving nutrition, weight loss and fitness. You can find other related information on the website at:
www.theweightlossresource.com