By
updated 8/2/2011 5:14:57 PM ET 2011-08-02T21:14:57

When dieters starve themselves of calories, they starve their brain cells as well. New research finds that these hungry brain cells then release "feed me" signals, which drive hunger, slow metabolism and may cause diets to fail.

When the researchers created mice whose brain cells couldn't send out the signals, or appetite-increasing proteins, and these mice were leaner and ate less than normal after being starved.

"We generated a mouse that lacked this process in these neurons," study researcher Rajat Singh, of Albert Einstein College of Medicine in the Bronx, New York, said. "What we find is these mice eat less in response to a starvation challenge; they are leaner and they are healthier."

  1. Don't miss these Health stories
    1. Splash News
      More women opting for preventive mastectomy - but should they be?

      Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

    2. Larry Page's damaged vocal cords: Treatment comes with trade-offs
    3. Report questioning salt guidelines riles heart experts
    4. CDC: 2012 was deadliest year for West Nile in US
    5. What stresses moms most? Themselves, survey says
The results likely would apply to humans, as mice are often used as biological models for us, the researchers say; even so, further research is needed to confirm the same process occurs in humans.

Starving the brain
The starvation mechanism and feelings of hunger produced by these neurons is signaled through a process called autophagy (which literally means "self-eating") in which the cell breaks down its used parts. It does this to recycle the used parts, but also to harvest energy.

Most brain cells keep their autophagy at a steady level and don't respond to starvation. These appetite-sensing neurons are different, the researchers found, and are now the only known brain cells to ramp up autophagy in times of starvation.

    1. Snow-vember Surprise: Why Deep South Is Seeing Frosty Weather
    2. Creative Thinkers More Likely to Cheat
    3. How Morning Snacking Could Damage Your Diet
    4. 'UFOs' Disrupting Search for 'God Particle'
    5. 'Perfect' Celebrity Photos to Get Reality Check

This increased breakdown increases cellular levels of compounds called free fatty acids. Higher levels of fatty acids signal these special brain cells to release the appetite-inducing protein, which is called agouti-related peptide (AgRP).

"These neurons sense nutrients in the body and tell the body it's time to eat, time to stop eating," Singh told LiveScience. "When you are hungry, there is this process in the brain that gets upregulated and that makes you eat."

Body Odd: Why diet food is so unsatisfying

Turning down appetite
When the researchers turned off autophagy in the hypothalamus of mice, AgRP levels stayed low, as did levels of free fatty acids. These changes stopped the hunger signaling during times of starvation. When compared with normal mice, the mutant mice were about 10 percent leaner, were able to burn more energy, were more active and also ate less after food was withheld.

Because this AgRP protein is only expressed in these appetite-controlling neurons, blocking this process should only affect the appetite signaling, not the cellular breakdown and use of stored energy in other parts of the body.

If the process works the same way in humans as it does in mice, interrupting this pathway could help curb hunger and obesity. The researchers are continuing to study these mice and how disrupting this pathway changes their eating habits.

"These mice eat less in response to a starvation challenge, they are leaner and they are healthier," Singh said. "It has tremendous relevance to fighting obesity."

The study was published Aug. 2 in the journal Cell Metabolism.

© 2012 LiveScience.com. All rights reserved.

Video: Foods to ‘Cure’ aches, pains, insomnia and more

  1. Closed captioning of: Foods to ‘Cure’ aches, pains, insomnia and more

    >>> this morning on "eat smart today" the food you choose has a direct effect on your waistline and cholesterol but also impacts your mood and sleeping patterns. "today's" nutritionist is here with a revised and updated rendition of "joe bauer's food cures." joy, good morning. revised and updated because there is so much more new research.

    >> yes. and so the first book came out in 2007 and since then we've had a wealth of scientific information that really does show food is more than calories. it's nature's medicine. and in the book i show people that everyday foods can really help to manage, treat, sometimes even reverse common health conditions. it's pretty cool.

    >> fror example, you say eating the right foods can help aches and pains?

    >> yes, first, one of my top foods is ginger. ginger contains compounds that are similar to anti-inflammatory medication. relieve everyday soreness or joint inflammation that we'll suffer from. you can take a few slices and steep it in hot water for ginger tea or throw it into a stir fry or ground ginger in smoothies. it's terrific.

    >> red peppers have a tremendous amount of vitamins. one pepper gets 250 --

    >> 250% of our daily allotment for vitamin c. the reason i have it on our aches and pains table is because a study showed that people who tend to get arthritis have lower levels of vitamin c. so i say half of a red bell pepper a day going to be really good. and then pumpkin. pumpkin gets --

    >> she seems so happy talking about pumpkin.

    >> i love pumpkin. bright orange color from two potent caroteniods and helps reduce inflammation as well which means your joints are going to be happier and less painful.

    >> speaking of happy, let's talk about foods that are supposed to boost our mood.

    >> number one happy food has to be lentils. and that's because when we have volatile swings in our blood sugar , we're cranky, we're irritable and we're tired. and lentils has this winning dualal of fiber and protein which smooths out blood sugars and essentially keeps us feeling happy. salmon is another key player because it's got omega 3 fats and vitamin d. both have been linked to better moods. for people who have these types of issues, salmon at least twice a week. and oranges would be your fruit of choice because it has folate. folate is involved in making special brain chemicals to keep our regulation intact.

    >> another reason to have hopefully fresh squeezed orange juice in the morning. foods to help minimize pms .

    >> women, pay attention. first it's going to be yogurt. that's because we have research that shows women who struggle with severe pms symptoms tend to have lower levels of calcium one to two weeks prior to their period. yogurt is the top source of calci calcium. whether it's plain, flavored, traditional or greek. yogurt rocks. the next thing is almonds. almonds are rich in magnesium. magnesium has been shown to alleviate pms -induced headaches. the last thing is pineapple. pineapple has something that helps to relieve pms symptoms. it's also very juicy. when you bring water into your body it will flush water out which is great forgetting rid of water retention . sweet and delicious, helps with the cravings right around pms .

    >> it will all work well together in smoothie. almonds, how many do you need to eat to prevent the pain of pms ?

    >> a handful a day. that's all. you don't want to go overboard because you don't want to gain weight.

    >> preventing insomnia. unusual choices.

    >> when it comes to insomnia right off the bat i do have to say you want to layoff the caffeine eight hours before you hit the sack. you don't want to have a heavy fatty meal right before bed because that's going to disresult sleep for sure. we do know if you have a light p.m. snack, about 150 calories. atsz co it's a combination of turkey, milk, or cheese, together with carbohydrates you can producer is serotonin in the brain which lems you g helps you get a better night's sleep. here a scoop of cottage cheese with cinnamon or apple slices or rice cake with a spread of humus and a turkey slice. i would say within within hour. it would help. the key is get rid of that cough 15.

    >> we'll try your tips. thanks so much. joy bauer this

Discuss:

Discussion comments

,

Most active discussions

  1. votes comments
  2. votes comments
  3. votes comments
  4. votes comments