Tips Today The Representative For The Nutrient Vantage Hypothesis Of Obesity, Purpose I
Introduction
When y'all desire to investigate something using the scientific method, offset y'all do a model that y'all promise describes a natural phenomenon-- this is called a hypothesis. Then y'all become most testing that model against reality, nether controlled conditions, to run into if it has whatsoever predictive power. There is rarely a unmarried experiment, or unmarried study, that tin demonstrate that a hypothesis is correct. Most of import hypotheses involve many mutually buttressing lines of evidence from multiple enquiry groups earlier they're widely accepted. Although it's non necessary, agreement the machinery yesteryear which an number occurs, as well as having that machinery survive consistent amongst the hypothesis, adds substantially to the case.
With that inwards mind, this postal service volition become into greater exceptional on the evidence supporting nutrient vantage as well as palatability every bit major factors inwards the rule of nutrient intake as well as trunk fatness. There is a large sum of supportive evidence at this point, which is chop-chop expanding due to the efforts of many bright researchers, withal for the sake of clarity as well as brevity, thence far I've entirely given a "tip of the iceberg" thought of it. But at that topographic point are 2 types of people who desire to a greater extent than detail: (1) the skeptics, as well as (2) scientifically inclined people who desire mechanism. This postal service is for them. It volition larn technical at times, every bit at that topographic point is no other agency to bring the cloth effectively.
First, to a greater extent than or less definitions. One of the problems amongst nutrient vantage is it's defined differently yesteryear unlike people, fifty-fifty researchers, as well as frequently it isn't defined at all. As defined inwards previous posts, I utilization the term nutrient vantage to refer specifically to the motivational value of food, i.e. its mightiness to reinforce behavior. For example, acquiring a gustation that causes a mortal to seek out the nutrient inwards inquiry to a greater extent than often. This is how some, simply non all, researchers define the term. Others utilization the term "food reward" to refer to both the motivational as well as the palatability value of food. Palatability refers specifically to the enjoyment derived from a food, too called its hedonic value. Palatability as well as vantage typically go together, simply non always.
The nutrient vantage hypothesis of obesity states that the vantage (reinforcing, motivational) as well as hedonic (pleasure, palatability) value of nutrient influence nutrient intake as well as trunk fatness, contributing to the evolution of obesity. Quite a fleck is known most the key nervous organisation (CNS, i.e. brain) circuitry that underlies vantage as well as hedonic processing, as well as how this circuitry influences nutrient intake as well as trunk fatness. Most of the enquiry on vantage as well as hedonic processing began amongst the written report of drug addiction inwards animals as well as humans, withal these circuits evolved to guide behaviors that get upwardly fitness inwards the natural surroundings such every bit those relating to nutrient as well as sex, as well as enquiry too focuses on these processes.
Although nutrient vantage as well as nutrient palatability typically occur together, they are non the same thing. In the 1990s, Dr. Kent Berridge proposed that behavioral as well as CNS responses to nutrient tin survive divided into "wanting", corresponding to the reward/motivational aspects of food, as well as "liking", corresponding to the hedonic/palatability aspects of food, as well as this framework has been a practiced lucifer for the evidence since thence (1). These 2 elements tin survive separated from 1 to a greater extent than or less other experimentally, as well as sometimes inwards daily life every bit well. One instance is a mortal who is addicted to a drug despite no longer deriving pleasance from it. This is a instance of potent "wanting" without "liking".
Brain Circuits as well as Neurotransmitters Underlying Food Reward as well as Hedonic Processing
The fact that the vantage as well as palatability value of nutrient tin survive experimentally dissociated implies that they are mediated yesteryear distinct CNS circuits. Indeed, although vantage as well as hedonic circuits overlap to to a greater extent than or less marking as well as influence 1 another, each organisation has its ain unique circuitry as well as suite of chemic neurotransmitters. CNS regions of import for vantage processing include the orbitofrontal cortex, amygdala, nucleus accumbens, dorsal striatum, ventral tegmental area, substantia nigra as well as the lateral hypothalamus (2). Dopamine signaling inwards these areas is a peculiarly of import ingredient of reward, simply has lilliputian deport upon on hedonic processes (3). Dopamine isn't thence much a pleasance chemic every bit it is a reward/motivation chemical.
CNS regions of import for processing food-related hedonic data include the brainstem, pons, nucleus accumbens, ventral pallidum, amygdala, insula as well as prefrontal cortex (4). Note that these overlap somewhat amongst encephalon regions that procedure vantage information, simply inwards to a greater extent than or less cases the subregions or neuron sub-populations that mediate these 2 processes are distinct fifty-fifty inside the same full general CNS region. Opioid signaling inwards these regions is a major factor inwards hedonic processing, simply has less deport upon on vantage functions (5, 6). Opioids, inwards certainly parts of the brain, are pleasance chemicals.
Another shape of chemic signals worth mentioning is the endocannabinoids. The endocannabinoid receptor CB1 was identified every bit the encephalon receptor for delta-9-THC, the primary psychoactive constituent of marijuana, as well as thence the endogenous ligands for the cannabinoid receptors were discovered (7). We at in 1 trial know that the primary 2 endogenous ligands are anandamide as well as 2-arachidonylglycerol, as well as the 2 receptors are CB1 as well as CB2. Endocannabinoid receptors are expressed inwards CNS regions related to vantage as well as hedonic processing, as well as they are known to survive involved inwards both processes.
In improver to these 3 chemic systems (dopamine, opioids as well as endocannabinoids), at that topographic point are other neurotransmitters that are intimately involved such every bit glutamate as well as GABA, simply these are not specific to vantage as well as hedonic processes since they are the primary excitatory as well as inhibitory neurotransmitters of the brain, respectively. So their interest inwards vantage as well as hedonic processing depends strictly on which neurons they're acting on.
Testing the Food Reward Hypothesis
If the nutrient vantage hypothesis is correct, nosotros should await to notice certainly things:
1. Increasing the reward/palatability value of the diet should campaign fatty arrive at inwards animals as well as humans.
2. Decreasing the reward/palatability of the diet should campaign fatty loss inwards animals as well as humans that send excess fat.
3. Individual sensitivity to nutrient vantage should predict time to come fatty gain.
4. Brain circuitry that controls motivational as well as hedonic processing should interact amongst circuits that command nutrient intake as well as trunk fatness.
5. Manipulation of vantage as well as hedonic circuits inwards the encephalon (e.g., yesteryear lesion, drugs or genetic manipulation) should deport upon nutrient intake as well as trunk fatness.
6. Genetic differences that influence vantage and/or hedonic circuits should correlate amongst differences inwards trunk fatness.
7. On a cultural level, obesity prevalence should runway amongst changes inwards the reward/palatability value of prevailing diet patterns.
In the side yesteryear side post, I volition explore whether or non the evidence is consistent amongst these predictions.
When y'all desire to investigate something using the scientific method, offset y'all do a model that y'all promise describes a natural phenomenon-- this is called a hypothesis. Then y'all become most testing that model against reality, nether controlled conditions, to run into if it has whatsoever predictive power. There is rarely a unmarried experiment, or unmarried study, that tin demonstrate that a hypothesis is correct. Most of import hypotheses involve many mutually buttressing lines of evidence from multiple enquiry groups earlier they're widely accepted. Although it's non necessary, agreement the machinery yesteryear which an number occurs, as well as having that machinery survive consistent amongst the hypothesis, adds substantially to the case.
With that inwards mind, this postal service volition become into greater exceptional on the evidence supporting nutrient vantage as well as palatability every bit major factors inwards the rule of nutrient intake as well as trunk fatness. There is a large sum of supportive evidence at this point, which is chop-chop expanding due to the efforts of many bright researchers, withal for the sake of clarity as well as brevity, thence far I've entirely given a "tip of the iceberg" thought of it. But at that topographic point are 2 types of people who desire to a greater extent than detail: (1) the skeptics, as well as (2) scientifically inclined people who desire mechanism. This postal service is for them. It volition larn technical at times, every bit at that topographic point is no other agency to bring the cloth effectively.
Baca Juga
First, to a greater extent than or less definitions. One of the problems amongst nutrient vantage is it's defined differently yesteryear unlike people, fifty-fifty researchers, as well as frequently it isn't defined at all. As defined inwards previous posts, I utilization the term nutrient vantage to refer specifically to the motivational value of food, i.e. its mightiness to reinforce behavior. For example, acquiring a gustation that causes a mortal to seek out the nutrient inwards inquiry to a greater extent than often. This is how some, simply non all, researchers define the term. Others utilization the term "food reward" to refer to both the motivational as well as the palatability value of food. Palatability refers specifically to the enjoyment derived from a food, too called its hedonic value. Palatability as well as vantage typically go together, simply non always.
The nutrient vantage hypothesis of obesity states that the vantage (reinforcing, motivational) as well as hedonic (pleasure, palatability) value of nutrient influence nutrient intake as well as trunk fatness, contributing to the evolution of obesity. Quite a fleck is known most the key nervous organisation (CNS, i.e. brain) circuitry that underlies vantage as well as hedonic processing, as well as how this circuitry influences nutrient intake as well as trunk fatness. Most of the enquiry on vantage as well as hedonic processing began amongst the written report of drug addiction inwards animals as well as humans, withal these circuits evolved to guide behaviors that get upwardly fitness inwards the natural surroundings such every bit those relating to nutrient as well as sex, as well as enquiry too focuses on these processes.
Brain Circuits as well as Neurotransmitters Underlying Food Reward as well as Hedonic Processing
The fact that the vantage as well as palatability value of nutrient tin survive experimentally dissociated implies that they are mediated yesteryear distinct CNS circuits. Indeed, although vantage as well as hedonic circuits overlap to to a greater extent than or less marking as well as influence 1 another, each organisation has its ain unique circuitry as well as suite of chemic neurotransmitters. CNS regions of import for vantage processing include the orbitofrontal cortex, amygdala, nucleus accumbens, dorsal striatum, ventral tegmental area, substantia nigra as well as the lateral hypothalamus (2). Dopamine signaling inwards these areas is a peculiarly of import ingredient of reward, simply has lilliputian deport upon on hedonic processes (3). Dopamine isn't thence much a pleasance chemic every bit it is a reward/motivation chemical.
CNS regions of import for processing food-related hedonic data include the brainstem, pons, nucleus accumbens, ventral pallidum, amygdala, insula as well as prefrontal cortex (4). Note that these overlap somewhat amongst encephalon regions that procedure vantage information, simply inwards to a greater extent than or less cases the subregions or neuron sub-populations that mediate these 2 processes are distinct fifty-fifty inside the same full general CNS region. Opioid signaling inwards these regions is a major factor inwards hedonic processing, simply has less deport upon on vantage functions (5, 6). Opioids, inwards certainly parts of the brain, are pleasance chemicals.
Another shape of chemic signals worth mentioning is the endocannabinoids. The endocannabinoid receptor CB1 was identified every bit the encephalon receptor for delta-9-THC, the primary psychoactive constituent of marijuana, as well as thence the endogenous ligands for the cannabinoid receptors were discovered (7). We at in 1 trial know that the primary 2 endogenous ligands are anandamide as well as 2-arachidonylglycerol, as well as the 2 receptors are CB1 as well as CB2. Endocannabinoid receptors are expressed inwards CNS regions related to vantage as well as hedonic processing, as well as they are known to survive involved inwards both processes.
In improver to these 3 chemic systems (dopamine, opioids as well as endocannabinoids), at that topographic point are other neurotransmitters that are intimately involved such every bit glutamate as well as GABA, simply these are not specific to vantage as well as hedonic processes since they are the primary excitatory as well as inhibitory neurotransmitters of the brain, respectively. So their interest inwards vantage as well as hedonic processing depends strictly on which neurons they're acting on.
Testing the Food Reward Hypothesis
If the nutrient vantage hypothesis is correct, nosotros should await to notice certainly things:
1. Increasing the reward/palatability value of the diet should campaign fatty arrive at inwards animals as well as humans.
2. Decreasing the reward/palatability of the diet should campaign fatty loss inwards animals as well as humans that send excess fat.
3. Individual sensitivity to nutrient vantage should predict time to come fatty gain.
4. Brain circuitry that controls motivational as well as hedonic processing should interact amongst circuits that command nutrient intake as well as trunk fatness.
5. Manipulation of vantage as well as hedonic circuits inwards the encephalon (e.g., yesteryear lesion, drugs or genetic manipulation) should deport upon nutrient intake as well as trunk fatness.
6. Genetic differences that influence vantage and/or hedonic circuits should correlate amongst differences inwards trunk fatness.
7. On a cultural level, obesity prevalence should runway amongst changes inwards the reward/palatability value of prevailing diet patterns.
In the side yesteryear side post, I volition explore whether or non the evidence is consistent amongst these predictions.
