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Apr. 14th, 2021
I really like this Gut Reactions book!
Apr. 14th, 2021 07:48 pmFrom the chapter on Ghrelin:
The hormone ghrelin is produced in the stomach, and acts in a way opposite to leptin. Leptin produced in fat cells decreases appetite; ghrelin increases appetite. Ghrelin also decreases the rate at which we burn glucose and fat. It tells the body it's running out of food so stop wasting it. when we become insulin-resistant, high levels of insulin in the blood interfere with ghrelin's signals. Insulin's job is to get rid of blood sugar, so it reduces the amount of ghrelin, and the muscles keep burning glucose and fat.
Thyroid hormone, which regulates metabolism, has a similar effect, reducing ghrelin so that more fuel is burned. People with overactive thyroid glands burn energy faster. As we get fatter, ghrelin production declines. This makes sense, since we have plenty of stored energy, we don't need a signal to eat more. The problem is that often the reason we get fat is that are eating when we aren't hungry, not because ghrelin is telling us to eat. So we continue to eat when we aren't hungry, and we get fat enough to become leptin resistant [this is discussed earlier in the book - obesity creates leptin resistance, so that once someone becomes obese, they always feel hungry, because the leptin "fullness" signal is never heard by their body] and we become hungry all the time.
Ghrelin is produced in the stomach in its inactive form. It is activated by the addition of a medium-chain fatty acid usually artoenin, to the ghrelin molecule. During fasting, mobilization of free fatty acids occurs, and upon feeding, this mobilization is suppressed, and this leads to more activated ghrelin during fasting. When ghrelin stimulates appetite, it stimulates a desire for fats more than for protein or carbohydrate [my note: this is so cool to read because when I was calorie restricting for long periods of fasting, sometimes 24 hours last year, I noticed that when I did get hungry, I would want nothing but nuts, which are high in fat]. Contrast this with neuropeptide Y, the powerful appetite stimulating hormone that causes a preference for carbohydrate. Glucogon reduces levels of ghrelin. This happens in lean and obese individuals, however in obese individuals this reduction in ghrelin does not cause satiety as it does in lean people. Obese people remain hungry. They appear to be resistant to the appetite suppressing power of glucogon, despite the lower ghrelin levels.
Ghrelin is mainly produced in the stomach, but it is also produced in the upper digestive tract, the lungs, the pancreas, the gonads, the adrenal cortex, the placenta, the brain, and the kidneys. Ghrelin receptors are found in other tissues, notably the lining of the arteries, where ghrelin protects against atherosclerosis. Ghrelin is not just an appetite stimulant, it also manages the output side of the energy equation. It adjusts the amount of energy going into fat storage, glycogen storage, and into creating body heat. It also adjusts the mechanical sensors in the stomach that tell us whether the stomach is distended or not. The more ghrelin there is, the less sensitive we are to a full stomach. This is why when we eat too quickly, it is easy to over-eat. The ghrelin levels have not had a chance to fall, so we are not as sensitive to the pressure signals we are getting from the stomach.
Ghrelin's actions in the brain are not limited to appetite control in the hypothalamus. Ghrelin also effects the dopamine circuits in the brain's reward center, which control addiction. Without ghrelin, there is no reward for alcohol or highly palatable foods. Limiting deserts and alcohol to times when we have low ghrelin levels, such as when we are full, may help to reduce the addictive nature of these consumables.
Ghrelin has anti-depression effects and it decreases anxiety. Ghrelin as an appetite stimulant, increases the number of meals but not the size of the meals. after a fast, eating a meal slowly enough to allow ghrelin levels to rise, will thus prevent over-eating. When we gain weight, ghrelin levels drop. When we lose weight, ghrelin levels rise. This is one mechanism the body has for maintaining body fat levels (homeostasis).
Ghrelin inhibits the release of insulin after a meal. If you eat only when you are hungry, the glucose will get into your system, but the insulin will take its time. If you get carbohydrates when you aren't feeling hungry, insulin levels spike, causing all the problems associated with metabolic syndrome, obesity, and diabetes.
Ghrelin has anti-inflammatory effects, and helps cells grow despite stress. It is being considered a therapy for colitis encepsis. It also helps the stomach regenerate after injury to its mucosal layers.
The ghrelin receptor controls a whole raft of biological functions besides those mentioned above. It releases human grown hormone (hgh), it modulates sugar and fat metabolism, it regulates gastro-intestinal motility, making food move through your digestive system better, it protects neurons and cardiovascular cells, and it regulates the immune system.
All these benefits come from feeling hungry. If you aren't feeling hungry several times a day, you are missing out on the benefits of ghrelin.
But wait! There's more! Ghrelin acts on the brain's hippocampus to increase learning and memory. This is important to any organism that wants to remember where to find food or which food made it sick. If you want to learn something, learn it while your stomach is growling. Fasting for three or four meals makes a difference in brain function, learning, and memory. But just skipping the snacks between meals can also help, as well as lowering your insulin levels to prevent insulin resistance.
Ghrelin actually helps you form new brain cells, even in adulthood. It may also be that the low ghrelin levels experienced in obese people, are what leads to the non-Alzhiemer's dementia that is associated with obesity.
The next time you feel hungry, think of all the good things ghrelin is doing for your body, and see if you can prolong the feeling for a while. Not only will you be healthier and smarter, but you will also lose a little weight.
The hormone ghrelin is produced in the stomach, and acts in a way opposite to leptin. Leptin produced in fat cells decreases appetite; ghrelin increases appetite. Ghrelin also decreases the rate at which we burn glucose and fat. It tells the body it's running out of food so stop wasting it. when we become insulin-resistant, high levels of insulin in the blood interfere with ghrelin's signals. Insulin's job is to get rid of blood sugar, so it reduces the amount of ghrelin, and the muscles keep burning glucose and fat.
Thyroid hormone, which regulates metabolism, has a similar effect, reducing ghrelin so that more fuel is burned. People with overactive thyroid glands burn energy faster. As we get fatter, ghrelin production declines. This makes sense, since we have plenty of stored energy, we don't need a signal to eat more. The problem is that often the reason we get fat is that are eating when we aren't hungry, not because ghrelin is telling us to eat. So we continue to eat when we aren't hungry, and we get fat enough to become leptin resistant [this is discussed earlier in the book - obesity creates leptin resistance, so that once someone becomes obese, they always feel hungry, because the leptin "fullness" signal is never heard by their body] and we become hungry all the time.
Ghrelin is produced in the stomach in its inactive form. It is activated by the addition of a medium-chain fatty acid usually artoenin, to the ghrelin molecule. During fasting, mobilization of free fatty acids occurs, and upon feeding, this mobilization is suppressed, and this leads to more activated ghrelin during fasting. When ghrelin stimulates appetite, it stimulates a desire for fats more than for protein or carbohydrate [my note: this is so cool to read because when I was calorie restricting for long periods of fasting, sometimes 24 hours last year, I noticed that when I did get hungry, I would want nothing but nuts, which are high in fat]. Contrast this with neuropeptide Y, the powerful appetite stimulating hormone that causes a preference for carbohydrate. Glucogon reduces levels of ghrelin. This happens in lean and obese individuals, however in obese individuals this reduction in ghrelin does not cause satiety as it does in lean people. Obese people remain hungry. They appear to be resistant to the appetite suppressing power of glucogon, despite the lower ghrelin levels.
Ghrelin is mainly produced in the stomach, but it is also produced in the upper digestive tract, the lungs, the pancreas, the gonads, the adrenal cortex, the placenta, the brain, and the kidneys. Ghrelin receptors are found in other tissues, notably the lining of the arteries, where ghrelin protects against atherosclerosis. Ghrelin is not just an appetite stimulant, it also manages the output side of the energy equation. It adjusts the amount of energy going into fat storage, glycogen storage, and into creating body heat. It also adjusts the mechanical sensors in the stomach that tell us whether the stomach is distended or not. The more ghrelin there is, the less sensitive we are to a full stomach. This is why when we eat too quickly, it is easy to over-eat. The ghrelin levels have not had a chance to fall, so we are not as sensitive to the pressure signals we are getting from the stomach.
Ghrelin's actions in the brain are not limited to appetite control in the hypothalamus. Ghrelin also effects the dopamine circuits in the brain's reward center, which control addiction. Without ghrelin, there is no reward for alcohol or highly palatable foods. Limiting deserts and alcohol to times when we have low ghrelin levels, such as when we are full, may help to reduce the addictive nature of these consumables.
Ghrelin has anti-depression effects and it decreases anxiety. Ghrelin as an appetite stimulant, increases the number of meals but not the size of the meals. after a fast, eating a meal slowly enough to allow ghrelin levels to rise, will thus prevent over-eating. When we gain weight, ghrelin levels drop. When we lose weight, ghrelin levels rise. This is one mechanism the body has for maintaining body fat levels (homeostasis).
Ghrelin inhibits the release of insulin after a meal. If you eat only when you are hungry, the glucose will get into your system, but the insulin will take its time. If you get carbohydrates when you aren't feeling hungry, insulin levels spike, causing all the problems associated with metabolic syndrome, obesity, and diabetes.
Ghrelin has anti-inflammatory effects, and helps cells grow despite stress. It is being considered a therapy for colitis encepsis. It also helps the stomach regenerate after injury to its mucosal layers.
The ghrelin receptor controls a whole raft of biological functions besides those mentioned above. It releases human grown hormone (hgh), it modulates sugar and fat metabolism, it regulates gastro-intestinal motility, making food move through your digestive system better, it protects neurons and cardiovascular cells, and it regulates the immune system.
All these benefits come from feeling hungry. If you aren't feeling hungry several times a day, you are missing out on the benefits of ghrelin.
But wait! There's more! Ghrelin acts on the brain's hippocampus to increase learning and memory. This is important to any organism that wants to remember where to find food or which food made it sick. If you want to learn something, learn it while your stomach is growling. Fasting for three or four meals makes a difference in brain function, learning, and memory. But just skipping the snacks between meals can also help, as well as lowering your insulin levels to prevent insulin resistance.
Ghrelin actually helps you form new brain cells, even in adulthood. It may also be that the low ghrelin levels experienced in obese people, are what leads to the non-Alzhiemer's dementia that is associated with obesity.
The next time you feel hungry, think of all the good things ghrelin is doing for your body, and see if you can prolong the feeling for a while. Not only will you be healthier and smarter, but you will also lose a little weight.