Five-Minute Stress Relief.com

Leptin and Ghrelin – Hormones of Hunger and Fullness

This subject has all the aspects of a good mystery with its solution leading to a kind of fountain of youth. While science has struggled to understand the mysteries of the human body, this journey’s conclusion holds a vital key to weight control and possessing a youthful, slim body.

Ghrelin

Ghrelin was discovered in 1999, a hormone produced by cells lining the stomach that stimulate appetite. Acting as a counterpart to Leptin, levels of ghrelin follow a diurnal circadian rhythm – increasing from midnight to dawn in average people. Ghrelin is the reason we wake up hungry.

Leptin

Leptin is produced by adipose tissue (fat cells) and acts as a signal to the brain to stop eating. Leptin binds a receptor site in the hypothalamus, signaling the brain fat stores are adequate. Levels of leptin are lower when you're thin and higher when you're fat. In 1994, when it was first discovered, the finding was greeted with great enthusiasm and the grand wish was that extra weight would just “dissolve away” if obese people were given leptin. However, it soon became evident that the issue of being overweight was way more complicated that first thought.

The Mystery

Here’s where the mystery develops. It seems that many obese people have built up a resistance to the appetite-suppressing effects of leptin. In much the same way that people with type 2 diabetes have become resistant to the effects of insulin, high concentrations of leptin (from the enlarged fat stores in overweight people) result in cells that normally respond to leptin becoming desensitized. And how leptin signaling is turned off in the body was not known, only that insulin and leptin are the major hormones regulating metabolism.

A Second Subtance

Then more research, published in the journal Devlopmental Cell, found that a second substance, a signaling protein, protein tyrosine phosphatase (PTP1B) exhibited activity in the "appetite center" in the brain, so as to increase sensitivity to leptin. Also it was found that leptin has very powerfully influence on energy utilization and fat burning via its effects on the hypothalamus and the sympathetic nervous system; and that leptin not only changes brain chemistry, it also "rewires" these very important areas of the brain that control hunger and metabolism.

The Desensitizing Process

As more studies were done and published in prestigious journals like the American Journal of Clinical Nutrition, it was confirmed that obese people do not lack leptin – they actually have higher-than-normal levels. So how does this desensitizing process occur? When one isn’t really hungry, but is indulging in comfort eating or binging, leptin's message (which normally reduces hunger and fat stores and increases fat burning) doesn’t get through to the brain, so one stays hungry and stores more fat, rather than burning it.

The extra fat produces more leptin, and this hormonal surge and overexposure disrupts the body’s regulation of glucose homeostasis (signaling the liver what to do with its stored glucose). And these surges result in leptin-resistance – just as it happens in insulin-resistance. Leptin resistance causes an increase in visceral fat (See Deadly Dangers of Fats and Sweets – Visceral Fat Verses Subcutaneous Fat). This further smothers the liver from receiving proper hormonal signals.

As sugar gets metabolized in fat cells, fat releases additional surges in leptin, disrupting the liver's capacity to respond properly, causing your liver to manufacture too much sugar from protein.

Effects on the Sympathetic Nervous System

Oddly enough, the master control of the sympathetic nervous system in the brain does not become leptin-resistant and continues to respond the signals of elevated leptin, causing over-stimulation of the sympathetic nervous system; so one stays hungry, continues to get fatter, and gets elevated sugar, insulin resistance, diabetes, high blood pressure, heart disease and accelerated aging.

Insulin and leptin resistance result in smaller and denser LDL (“bad” cholesterol) particles and an increase in their quantities. Small, dense LDL particles manage to lodge between the cells lining the inside of the arteries where they oxidize, turn rancid, and cause inflammation of the lining of the arteries and plaque formation. Scientific studies have shown a causal effect of elevated insulin and leptin on heart and vascular disease.

Food Cravings

Leptin also serves to reduce cravings for sweet foods by targeting taste receptors on the tongue. And the body's failure to respond to the leptin’s hormonal signals increases the 'sweet tooth' craving that affects so many people and in is most likely why some people are more prone to eat calorie-rich sweet foods.

Sleep, Stress and Leptin

Further research at the University of Chicago (published in The Journal of Clinical Endocrinology & Metabolism) has found that sleep deprivation plays an important role in regulating leptin levels and in controlling appetite. During sleep, leptin levels normally rise, however they are very sensitive to sleep duration. When the University of Chicago's sleep laboratory tested volunteers, they were monitored to receive the same amount of calories and activity and, therefore, leptin levels and appetite control should not have changed. However the study showed a major change took place.

When sleep was restricted, leptin levels went down and ghrelin levels went up. After a six-day sleep deprivation period, volunteers had a leptin decreases ranging from 19% to 26%, verifying that sleep deprivation results in a triggering of hormones of the sympathetic nervous system, which lowers leptin levels. The volunteer’s appetite also increased proportionally with their desire for high carbohydrate, calorie-dense foods increased by an astounding 45%!

What’s more, those who slept under eight hours a night not only had lower levels of leptin and higher levels of ghrelin, they also showed a higher level of body fat, which seemed to correlate with their sleep patterns. And in a larger study of more than 1,000 volunteers, the results showed a nearly identical appetite control pattern.

In fact, the probability of gaining weight rises as the number of hours an individual sleeps decreases. When one sleeps less than six hours a night, they are 50 % more likely to become obese than someone who’s getting seven to eight hours sleep each night.

The Solution

Okay, now that you’re feeling overwhelmed, as most of Americans are lacking in sufficient sleep and are overweight, relief is in site. Additional research studies have found that a combination of diet and exercise can make large changes in leptin levels occur.

In fact, when the scientists factored in the amount of fat lost during their studies, leptin levels had dropped more than they anticipated. It seems that long-term diet and exercise programs may directly affect the plasma-leptin ratio due to changes in fat mass. Long-term reductions in leptin levels appear to rebalance the manner in which the central nervous system regulates appetite and metabolism.

So the encouraging message here is that it’s really all in your control. Dedicating yourself to an effective diet and exercise program can not only result in lost pounds and enhanced appearance, it can be a driving force that reverses the path of your health, wellbeing and longevity.

© 2009 Five-Minute Stress Relief - All Rights Reserved

Sources: Dynamics of Leptin and Endocrine Function National Institutes of Health Clinical Center (http://clinicaltrials.gov/ ct2/show/NCT00001543) Leptin Resistance and Obesity Obesity (2006) 14, 254S–258S; doi: 10.1038/oby.2006.319 Leptin Increases Circulating Glucose, Insulin and Glucagon via Sympathetic Neural Activation in Fasted Mice International Journal of Obesity June 1999, Volume 23, Number 6, Pages 660-665 Metabolic Consequences of Sleep Restoration Sleep Disorders Research Advisory Board Meeting Minutes June 26, 2002 National Center on Sleep Disorders Research National Heart, Lung, and Blood Institute (www.nhlbi.nih.gov/meetings/sdrab/02-06-26.htm)

Print PDF Page for: Leptin and Ghrelin Hormones of Hunger and Fullness