Leptin and Ghrelin and Diet Sodas....

Leptin

Leptin (Greek leptos meaning thin) is a protein hormone that plays a key role in regulating energy intake and energy expenditure, including appetite and metabolism. Leptin is one of the most important adipose derived hormones. Leptin binds to NPY(Neuropeptide Y) neurons in the arculate nucleus, in such a way that decreases the activity of these neurons. Leptin signals to the brain that the body has had enough to eat, or satiety.

Although leptin is a circulating signal that reduces appetite, in general, obese people have an unusually high circulating concentration of leptin. These people are said to be resistant to the effects of leptin, in much the same way that people with type 2 diabetes are resistant to the effects of insulin. The high sustained concentrations of leptin from the enlarged adipose stores result in leptin desensitization.

Signs that your body has too much leptin and you may have become resistant to it.
1. Constant hunger
2. Diabetes
3. Elevated thyroid hormones
4. Heart disease
5. High blood pressure
6. Higher cholesterol
7. Increased inflammation
8. Obesity

Ghrelin

Ghrelin is a hormone produced mainly by P/D1 cells lining the fundus of the human stomach and epsilon cells of the pancreas that stimulates hunger. Ghrelin levels increase before meals and decrease after meals. It is considered the counterpart of the hormone leptin, produced by adipose tissue, which induces satiation when present at higher levels. Ghrelin has emerged as the first circulating hunger hormone. Ghrelin and synthetic ghrelin mimetics (the growth hormone secretagogues) increase food intake and increase fat mass by an action exerted at the level of the hypothalamus.

Tying the two together.

The fluctuation of leptin and ghrelin hormone levels results in the motivation of an organism to consume food. When an organism eats, adipocytes trigger the release of leptin into the body. Increasing levels of leptin results in a reduction of one's motivation to eat. After hours of non-consumption, leptin levels drop significantly. These low levels of leptin cause the release of secondary hormone, ghrelin, which in turn reinitiates the feeling of hunger.

There is the hunger cycle in a nutshell. Leptin stops the hunger essentially, while ghrelin starts the hunger. So how does this interpret to thin or fat/obese?

Two guys we will call one Joe and one Mike (these are totally made up names and have no reflection on anyone in any study or people I know). Joe is ave height and weight let's use 5'10" and 170lbs. Mike is also 5'10" and 260lbs.

First we need to know their BMI (Body Mass Index). Using the US formula (non metric) for calculating BMI: BMI = lb * 703 / in2. Joe is 170lbs and 70in tall, his BMI will be 170 * 703 / 4900 (in2) for a total of 24.4 BMI. Now Mike is 260lbs and 70in tall, so his BMI will be 260 * 703 / 4900 for a total of 37.3 BMI. For reference let's list the BMI scale for comparison:

BMI Classification
< 18.5 underweight
18.5–24.9 normal weight
25.0–29.9 overweight
30.0–34.9 class I obesity
35.0–39.9 class II obesity
> 40.0 class III obesity (sever obesity)
40.0-49.9 morbid obesity
> 50 super obese

Joe is on the high side of normal weight with 24.4 BMI, while Mike is in the class II obesity range with 37.3 BMI. So what does this mean in terms of Leptin and Ghrelin? People who are obese have been found to have higher levels of leptin in the bloodstream. Really? Yes, really. They become leptin resistant the same way a diabetic becomes insulin resistant. They do not get the full satiety effect that a person who is not obese would. Neuropeptide Y is never shut off in the brain and you still have hunger. This in turn keeps the ghrelin levels high since it is released in the stomach after emptying and not by the amount of leptin in the bloodstream. So the net affect is high blood levels of leptin due to leptin resistance, neuropeptide y stays active creating hunger and you eat then the stomach empties and produces gherlin causing more neuropeptide y to be relased, and guess what you are still hungry.

People who are not obese are usually not leptin resistant. They eat, leptin receptors are triggered and they fill full and satisified. Neuropeptide Y is shut off and the hunger is gone. Once the stomach empties, ghrelin is released causing the build up of neuropeptide y again and you get hungry and you eat. The cycle continues but on a normal and healthy scale.

Ok, so now we know the basic endocrinology of leptin and ghrelin for the purposes of this discussion. Again, this is put into a level of basic understanding and slanted for the use of this discussion. Both leptin and ghrelin offer a bit more than just this, but these two hormones are key to the hunger/satiety cycle for all of us. How is this hunger/satiety cycle affected by diet soda? Let's start slow and work our way up the big stuff.

Most people who drink a diet soda are concerned with calories. It's true of all of us. We like the taste of soda but we don't want the empty calories. Diet Coke became the king of diet sodas in the mid 80's and never stopped. The problem with this is even though there are no calories there is a sweet taste. So how can something that tastes sweet but isn't be bad? Easy. Your brain! The human brain acts like a computer. Each sense we have whether it be touch, sight, hearing, smell and yes taste is essentially an input for the brain (our personal computer) to analyze. You feel cold because your brain tells you this. You see blue because your brain tells you something is blue. You taste sweet because your brain tells you it's sweet.

Now the artifical-sweeteners can trick the sugar receptors in your body and your brain can tell you its sweet, but the brain also can tell the difference between it and real sugar. It knows whether you can tell by taste or not. It also knows that since it is not real sugar and has no calories to account for, that it does not need to release leptin to feel satisfied and therefore you continue to try to satisfy your hunger.

So sweet taste with no calories to account for causes the body to search for those calories and if they are not there guess what (yeah you guessed it) the body will crave more. Ghrelin will increase and you are hungry again. Now you gain weight and leptin (released from fat cells) is released and continues to rise even more with each pound you put on. Ghrelin continues to be released as you are eating more and becoming leptin resistant. 10 years pass and you are 100 lbs overweight. Diet sodas and all foods containing artificial-sweeteners compound this cycle.

When will it stop?

When will you change?

Eat clean, don't drink diet sodas including diet sports drinks and exercise regularly to take back your health from the brink of obesity.



Sources: Wikipedia, Master Your Metabolism by Jillian Michaels and other online sources.