FREE NEWSLETTER: Econintersect sends a nightly newsletter highlighting news events of the day, and providing a summary of new articles posted on the website. Econintersect will not sell or pass your email address to others per our privacy policy. You can cancel this subscription at any time by selecting the unsubscribing link in the footer of each email.

posted on 28 September 2015

Chemical Messengers: How Hormones Make Us Feel Hungry And Full

from The Conversation

-- this post authored by Joseph Proietto, University of Melbourne

The need to find fuel to generate energy is a profound drive within the biology of all living organisms: we all need food to survive. So it's not surprising that our bodies have such a complex system to control food intake, driven by hormones.

Hormone levels also change when we lose weight. As much as we battle to trim down via diets and eating patterns, they're also the reason most of us will regain the weight we lose - or more.

The body's system for regulating food intake is coordinated by the hypothalamus, which is located under the midline of the brain, behind the eyes:

Within the hypothalamus are nerve cells that, when activated, produce the sensation of hunger. They do so by producing two proteins that cause hunger: neuropeptide Y (NPY) and agouti-related peptide (AGRP).

Quite close to these nerve cells is another set of nerves that powerfully inhibit hunger. They produce two different proteins that inhibit hunger: cocaine and amphetamine-regulated transcript (CART) and melanocyte-stimulating hormone (αMSH).

These two sets of nerve cells initiate and send hunger signals to other areas of the hypothalamus. So, whether you feel inclined to eat or not depends on the balance of the activity between these two sets of neurons.

But what determines which set of neurons dominates at any given time?

The activity is mainly controlled by hormones that circulate in the blood. These come from tissues in various parts of the body that deal with energy intake and storage, including the gut (which receives and digests the food), the fat (which stores the energy) and the pancreas (which makes hormones that are involved in energy storage, such as insulin).

Hormones in the blood

Let's take a closer look at how each of these blood-circulating hormones work.

Ghrelin is made in the stomach. It stimulates hunger by entering the brain and acting on the neurons in the hypothalamus to increase the activity of the hunger-causing nerve cells and reducing the activity of hunger-inhibiting cells. As the stomach empties, the release of ghrelin increases. As soon as the stomach is filled, it decreases.

Insulin-like peptide 5 (ILP-5) was found to stimulate hunger in 2014. It is the second circulating hormone to have this effect and is mainly produced in the colon. But we still don't know its physiological role.

Cholecystokinin (CCK) is produced in the upper small bowel in response to food and gives a feeling of fullness. It is released soon after food reaches the small bowel. Researchers have found CCK can stop a mouse from eating as soon as it's injected into the brain.

Peptide YY, glucagon-like peptide 1 (GLP-1), oxyntomodulin and uroguanilin are all made from the last part of the small bowel and make us feel full. They are released in response to food in the gut.

Leptin is the most powerful appetite-suppressing hormone and is made in fat cells. It was discovered in 1994. The more fat cells we have, the more leptin the body produces.

Amylin, insulin and pancreatic polypeptide are made in the pancreas. Studies in the United States have shown that when insulin enters the brain it inhibits hunger, telling the brain "there is enough energy in the body, take a rest".

Amylin, discovered in 1981, is made in the same cells that make insulin (the beta cells). It has been shown to inhibit food intake.

The exact role of pancreatic polypeptide is not yet known, but there is evidence that it inhibits hunger.

The hypothalamus also receives signals from pleasure pathways that use dopamine, endocannabinoids and serotonin as messengers, which influence eating behaviour.

Once full, the stomach reduces the desire to eat both by lowering ghrelin production and by sending a message to the hypothalamus. Ghrelin levels reach a low around 30 to 60 minutes after eating.

Levels of hormones that make us feel full - CCK, PYY, GLP-1, amylin and insulin - all increase following a meal to reach a peak about 30 to 60 minutes later.

All the hormones then gradually return to their fasting levels three to four hours after a meal.

How weight loss affects our hormones

Several studies have found that diet-induced weight loss is associated with hormone changes that, together, promote weight regain.

Following weight loss, leptin levels decrease profoundly. Other hormonal changes include increases in circulating ghrelin, GIP and pancreatic polypeptide and reductions in PYY and CCK. Almost all of these changes favour regaining lost weight, by increasing hunger, reducing satiety and improving the capacity to store fat. These hormonal changes seem to be present for at least one year after weight loss, leading to a persistent increase in hunger.

These findings suggest suppressing hunger after weight loss - preferably with a replacement of hormones - may help people maintain their new weight.

Several of these agents have recently been approved by different regulatory bodies in the United States, Europe or Canada, but only one - liraglutide - is a version of one of the naturally occurring appetite suppressants (GLP-1). The ideal medication to maintain weight loss would be a long-acting mixture of three or more of the blood-circulating hormones we examined above: leptin, amylin, GLP-1, PYY, CCK and oxyntomodulin.

But producing such a mixture is proving a considerable challenge, so researchers continue to investigate how this might be done.

This article is part of an occasional series, Chemical Messengers, on hormones and the body.

The ConversationJoseph Proietto, Professor of Medicine, University of Melbourne

This article was originally published on The Conversation. Read the original article.

>>>>> Scroll down to view and make comments <<<<<<

Click here for Historical News Post Listing

Make a Comment

Econintersect wants your comments, data and opinion on the articles posted.  As the internet is a "war zone" of trolls, hackers and spammers - Econintersect must balance its defences against ease of commenting.  We have joined with Livefyre to manage our comment streams.

To comment, using Livefyre just click the "Sign In" button at the top-left corner of the comment box below. You can create a commenting account using your favorite social network such as Twitter, Facebook, Google+, LinkedIn or Open ID - or open a Livefyre account using your email address.

You can also comment using Facebook directly using he comment block below.

Econintersect Contributors


Print this page or create a PDF file of this page
Print Friendly and PDF

The growing use of ad blocking software is creating a shortfall in covering our fixed expenses. Please consider a donation to Econintersect to allow continuing output of quality and balanced financial and economic news and analysis.

Take a look at what is going on inside of
Main Home
Analysis Blog
From Money Controlling People to People Controlling Money
Rising Tide Does Not Lift All Ships
News Blog
Infographic Of The Day: The Most Popular Jobs In A Decade
Early And Late Cycle Verdicts Are Baseless
The Surprising Divergence Of Employment And Capacity Utilization
The Slump In Undocumented Immigration To The United States
U.S. Productivity Growth Flowing Downstream
Your Light Bulbs Could Be Playing Havoc With Your Health - Here's Why
Mentions Of Trump And Clinton In Hip Hop Lyrics
Salary Is The Most Important Job Criterion
Can Switch Replicate Nintendos Past Success
The Numbers Behind The Zumwalt
Docking A Huge Cruise Ship Is More Complicated Than You Think
New Seasonal Outlook Updates from NOAA and JAMSTEC - Let's Compare Them.
Infographic Of The Day: Driving Into A Battery Powered Future
Investing Blog
FinTech Is Taking A Bite Out Of Banks
Options Early Assignment - Should You Worry?
Opinion Blog
The Beer Goggles Stock Market
US 2016 Election: Will US-China Relations Change
Precious Metals Blog
Preparing For Post-Election Social Unrest
Live Markets
21Oct2016 Market Close: Major US Indexes Close Flat On Low Volume, Crude Prices Resume Climb, US Dollar Stabilizes In Mid 98 Handle, Yes, Most Investors Are Worried Which Way This Market Will Go
Amazon Books & More

.... and keep up with economic news using our dynamic economic newspapers with the largest international coverage on the internet
Asia / Pacific
Middle East / Africa
USA Government

Crowdfunding ....



Analysis Blog
News Blog
Investing Blog
Opinion Blog
Precious Metals Blog
Markets Blog
Video of the Day


Asia / Pacific
Middle East / Africa
USA Government

RSS Feeds / Social Media

Combined Econintersect Feed

Free Newsletter

Marketplace - Books & More

Economic Forecast

Content Contribution



  Top Economics Site Contributor TalkMarkets Contributor Finance Blogs Free PageRank Checker Active Search Results Google+

This Web Page by Steven Hansen ---- Copyright 2010 - 2016 Econintersect LLC - all rights reserved