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A blog written for those whose interests more or less match mine.

Eating high-fat foods breaks the “I’m full” signal

with 3 comments

Ruth Williams writes in The Scientist:

A chronic high-fat diet is thought to desensitize the brain to the feeling of satisfaction that one normally gets from a meal, causing a person to overeat in order to achieve the same high again. New research published today (August 15) in Sciencehowever, suggests that this desensitization actually begins in the gut itself, where production of a satiety factor, which normally tells the brain to stop eating, becomes dialed down by the repeated intake of high-fat food.

“It’s really fantastic work,” said Paul Kenny, a professor of molecular therapeutics at The Scripps Research Institute in Jupiter, Florida, who was not involved in the study. “It could be a so-called missing link between gut and brain signaling, which has been something of a mystery.”

While pork belly, ice cream, and other high-fat foods produce an endorphin response in the brain when they hit the taste buds, according to Kenny, the gut also sends signals directly to the brain to control our feeding behavior. Indeed, mice nourished via gastric feeding tubes, which bypass the mouth, exhibit a surge in dopamine—a neurotransmitter promoting reinforcement in the brain’s reward circuitry—similar to that experienced by those eating normally.

This dopamine surge occurs in response to feeding in both mice and humans. But evidence suggests that dopamine signaling in the brain is deficient in obese people. Ivan de Araujo, a professor of psychiatry at the Yale School of Medicine, has now discovered that obese mice on a chronic high-fat diet also have a muted dopamine response when receiving fatty food via a direct tube to their stomachs.

To determine the nature of the dopamine-regulating signal emanating from the gut, Araujo and his team searched for possible candidates. “When you look at animals chronically exposed to high-fat foods, you see high levels of almost every circulating factor—leptin, insulin, triglycerides, glucose, et cetera,” he said. But one class of signaling molecule is suppressed. Of these, Araujo’s primary candidate was oleoylethanolamide. Not only is the factor produced by intestinal cells in response to food, he said, but during chronic high-fat exposure, “the suppression levels seemed to somehow match the suppression that we saw in dopamine release.”

Araujo confirmed oleoylethanol’s dopamine-regulating ability in mice by administering the factor via a catheter to the tissues surrounding their guts. “We discovered that by restoring the baseline level of [oleoylethanolamide] in the gut . . . the high-fat fed animals started having dopamine responses that were indistinguishable from their lean counterparts.”

The team also found that . . .

Continue reading.

Written by LeisureGuy

22 August 2013 at 12:32 pm

Posted in Food, Science

3 Responses

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  1. Good article and interesting research. But the conclusion is pretty nutty:

    “The good news, however, is that ‘there is no permanent impairment in the [animals’] dopamine levels,’ Araujo said. This suggests that if drugs could be designed to regulate the oleoylethanolamide–to-PPAR-a pathway in the gut, Kenny added, it could have “a huge impact on people’s ability to control their appetite.”

    With the exception of the severely life-threatening morbidly obese (500 lb. and up), why would it even remotely make sense to need drugs to control appetite? We’ve had no difficulty doing that for 50,000 years, but now need drugs in the last 30??? And 60% of the western population is now overweight, so the majority of people will need to be on drugs??? Kooky stuff!

    We have to get back to the question of what has changed in the last 30 years to drive the overconsumption of food on a global basis, and for my money, sugar and refined carbs embedded into every commercial foodstuff are prime candidates of culpability. I think that sugar is to the food industry what nicotine was to the cigarette industry; the magical addictive compound that would drive sales forward.

    Steve

    23 August 2013 at 3:02 am

  2. I noticed that as well. I thought that

    “The good news, however, is that ‘there is no permanent impairment in the [animals’] dopamine levels,’ Araujo said. This suggests that…

    would continue, “restoring a balanced diet by cutting back on high-fat foods enables the signal to be again perceived.” In other words, if the damage is not permanent, resuming a good diet would fix things. Why a drug?

    The answer, I imagine, is that there’s no money to be made if people simple resume a good diet. But selling them a drug? Good business.

    LeisureGuy

    23 August 2013 at 6:34 am

  3. I figured you’d have caught the silliness of the conclusion :-)

    Steve

    23 August 2013 at 2:16 pm


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