The nerve which tells us our stomach is full becomes desensitized in the obese. The hormone which normally signals fullness further desensitizes that nerve. It sounds as if our only hope to lose weight and keep it off is to carefully plan every day's food intake and eat according to our intellect, ignoring all body signals that we've not eaten enough. What a daunting prospect.
The way the stomach detects and tells our brains how full we are becomes damaged in obese people but does not return to normal once they lose weight, according to new research from the University of Adelaide.
Researchers believe this could be a key reason why most people who lose weight on a diet eventually put that weight back on.
... the nerves in the stomach that signal fullness to the brain appear to be desensitized after long-term consumption of a high-fat diet.
"A hormone in the body, leptin, known to regulate food intake, can also change the sensitivity of the nerves in the stomach that signal fullness. In normal conditions, leptin acts to stop food intake. However, in the stomach in high-fat diet induced obesity, leptin further desensitizes the nerves that detect fullness.
"These two mechanisms combined mean that obese people need to eat more to feel full, which in turn continues their cycle of obesity."
Associate Professor Page says they're not yet sure whether this effect is permanent or just long-lasting.
"We know that only about 5% of people on diets are able to maintain their weight loss, and that most people who've been on a diet put all of that weight back on within two years," she says.
"More research is needed to determine how long the effect lasts, and whether there is any way -- chemical or otherwise -- to trick the stomach into resetting itself to normal." [emphasis mine]
The National Weight Control Registry studies people who lose a lot of weight and keep it off.
Here are some strategies that work for these people:
-eat a low-calorie, lowfat diet. They lose weight in all sorts of ways including ketogenic diets, but a lowfat diet is what most often works to maintain weight loss.
-exercise about an hour/day
-weigh themselves often, many once a day
-don't eat more on weekends.
They are a disciplined bunch - being comfortable with monitoring oneself, helps.
"More research is needed to determine how long the effect lasts, and whether there is any way -- chemical or otherwise -- to trick the stomach into resetting itself to normal."
Finding a way to undo, not just intellectually work around, the damage, would be a good thing!!
This is research on mice. It certainly shouldn't be considered as definitive for human beings.
Good news, everyone! Research in mice found away to reverse the damage. (Yes, still in mice, Laura)
See Science magazine, Vol 341, August 16, 3013, "A Gut Lipid Messenger inks Excess Dietary Fat to Dopamine Deficiency", p 800-802. Synthesis of a gastrointestinal lipid messenger, oleoylethanolamine (OEA), is suppressed after prolonged high fat intake. That's the mechanism for decreased dopamine reward from normal foods. After researchers infused OEA into the high-fat fed mice, through an intraperitoneal catheter, it "restored gut-stimulated dopamine release". The mice began to eat normal chow again, and their dopamine release was restored.
Naturally they end with, "Whether this concept can be developed into a useful weight-loss strategy will require further research."
Even if an intraperitoneal catheter were required, that's not more invasive than gastric bypass surgery. I imagine they'll find a better method to deliver OEA. Meanwhile, at least there's hope for future treatment now that the mechanism has been uncovered. That's a far cry from the original article's "doomed to fail" title.
In the meantime, I've lost two pounds on my "anti-food addiction" diet. I think substituting low carb vegetables and salad for grain-based foods has been helpful. My husband has lost four pounds too, since we started, with his less stringent version.
There are various human satiety mechanisms. Some of them are related to fat intake, some to the volume of food you eat, some to insulin release that happens after eating protein or carbs,
Which satiety mechanism is being used most depends on one's diet - if you are eating a high-fat diet, the fat-related satiety mechanism is used more.
Slowly the satiety mechanism adjusts with a change of diet. Not right away - maybe a few weeks or months. I feel full after my lowfat meals, but someone used to a high-fat diet would likely not.
I think what these researchers are elucidating is the details of what goes on with these satiety mechanisms. But just having that knowledge from experience of how these satiety mechanisms change with time, may be all we need.