Psychophysiolog of eatingPsychophysiolog of eatingRadwan BanimustafaRadwan Banimustafa

HungerHunger

Hunger can be a strong motivator .Hunger can be a strong motivator .In people on semi starvation diets much of their thinking In people on semi starvation diets much of their thinking and dreaming is about food .and dreaming is about food .Depletion of nutrients from the body activates Depletion of nutrients from the body activates homeostatic mechanism to release stored food .homeostatic mechanism to release stored food .When the body stores are diminished to a point that the When the body stores are diminished to a point that the automatic homeostatic mechanisms can’t cope the automatic homeostatic mechanisms can’t cope the whole body is mobilized to seek food .whole body is mobilized to seek food .Internal signals of hunger : empty or aching pain in the Internal signals of hunger : empty or aching pain in the stomach with feeling of weakness .stomach with feeling of weakness .External signals : odor and sight of food, habits, social . External signals : odor and sight of food, habits, social .

Regulatory centers in the Regulatory centers in the hypothalamushypothalamus

Regulation of food is crucial to life that we have Regulation of food is crucial to life that we have several homeostatic controls .several homeostatic controls .Hypothalamus, located in the base of the brain Hypothalamus, located in the base of the brain directly close to other parts of CNS, has very directly close to other parts of CNS, has very rich blood supply (readily affected by chemical rich blood supply (readily affected by chemical state of the blood ).state of the blood ).Two hypothalamic Areas influence food intake .Two hypothalamic Areas influence food intake .

- The lateral hypothalamus (LH) initiates eating .- The lateral hypothalamus (LH) initiates eating .- The ventromedial hypoth.(VMH)inhibits eating .- The ventromedial hypoth.(VMH)inhibits eating .

There are two control systems integrated in the There are two control systems integrated in the hypothalamus :hypothalamus :

Short term control of food intakeShort term control of food intake

Variables which influence the hypothalamic control Variables which influence the hypothalamic control of immediate appetite: blood-sugar level, of immediate appetite: blood-sugar level, stomach fullness, and body temperature.stomach fullness, and body temperature.Low sugar and insulin injection increase food Low sugar and insulin injection increase food intake, injection of glucose inhibit eating . intake, injection of glucose inhibit eating . Hypothalamus Contains (glucoreceptors) cells Hypothalamus Contains (glucoreceptors) cells sensitive to the rate at which glucose passes sensitive to the rate at which glucose passes through them .through them .Glucoreceptors in VMH and LH respond Glucoreceptors in VMH and LH respond differently to the glucose level in the blood . differently to the glucose level in the blood .

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Digestion is a slow, eating is stopped long Digestion is a slow, eating is stopped long before it is transformed to sugar.before it is transformed to sugar.A full stomach signals to the brain that food is in A full stomach signals to the brain that food is in the way.the way.If food is injected directly to the stomach of If food is injected directly to the stomach of hungry animals, and allowed to eat freely, they hungry animals, and allowed to eat freely, they eat much less .eat much less .If food is removed from the stomach of a If food is removed from the stomach of a satiated animal it will eat to compensate for the satiated animal it will eat to compensate for the loss only.loss only.Apparently distension of the stomach stimulate Apparently distension of the stomach stimulate VMH and inhibit further eating. VMH and inhibit further eating.

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An empty stomach produces periodic An empty stomach produces periodic contractions of the stomach wall (hunger Pangs) contractions of the stomach wall (hunger Pangs) this stimulate LH to initiate eating. this stimulate LH to initiate eating.A third short term control mechanism is body A third short term control mechanism is body temperature .temperature .

- Most animals and humans eat less in a warm Most animals and humans eat less in a warm environment than in a cold one . environment than in a cold one .

- Cooling of the brain has similar effect .Cooling of the brain has similar effect .- LH responds to low brain temp. and VMH to high LH responds to low brain temp. and VMH to high

brain temp. brain temp.

Long term control of food intakeLong term control of food intake

Most wild animals maintain about the same weight through their Most wild animals maintain about the same weight through their lifetimes .lifetimes .It is more difficult for humans to do so because their eating is It is more difficult for humans to do so because their eating is influenced by emotional and social factors .influenced by emotional and social factors .The hypothalamus appears to regulate a delicate system which The hypothalamus appears to regulate a delicate system which stabilizes weight over time .stabilizes weight over time .Rats with damaged VMH overeat and become obese to a point, Rats with damaged VMH overeat and become obese to a point, then slow down eating. If diet is restricted they go to their original then slow down eating. If diet is restricted they go to their original weight, if they allowed to eat freely again they overeat and go back weight, if they allowed to eat freely again they overeat and go back to their obese weight .to their obese weight .If force-fed and become super obese then eat freely they reduce If force-fed and become super obese then eat freely they reduce their intake and return to their obese weight . their intake and return to their obese weight .

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Some correlates of body weight must act on the VMH to influence Some correlates of body weight must act on the VMH to influence food intake .food intake .Autopsies of animals with VMH lesions indicate that the amount of Autopsies of animals with VMH lesions indicate that the amount of fatty acids in the blood is influential .fatty acids in the blood is influential .In contrast rats with lesions in the LH refuse all food and water for In contrast rats with lesions in the LH refuse all food and water for some time after the operation and will die if not artificially fed ,after some time after the operation and will die if not artificially fed ,after few weeks they resume eating and drinking on their own ,but few weeks they resume eating and drinking on their own ,but stabilize at a lower weight level .stabilize at a lower weight level .These findings indicate that the VMH and the LH have reciprocal These findings indicate that the VMH and the LH have reciprocal effects on the (set point) for body weight .effects on the (set point) for body weight .Beside the hypothalamus Which plays a crucial regulatory role other Beside the hypothalamus Which plays a crucial regulatory role other brain areas like the limbic system and brain stem nuclei involved in brain areas like the limbic system and brain stem nuclei involved in smell and taste of food play a role too . smell and taste of food play a role too .

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The hypothalamus can be more The hypothalamus can be more accurately described as a critical link accurately described as a critical link between higher and lower brain areas that between higher and lower brain areas that regulate eating behavior rather than the regulate eating behavior rather than the areas containing feeding and satiety areas containing feeding and satiety centers . centers .

ObesityObesity

Is a major health problem .Is a major health problem .A popular view is that it stems from unresolved A popular view is that it stems from unresolved emotional problems .emotional problems .Research has failed to isolate a personality type Research has failed to isolate a personality type specific to obese people .specific to obese people .Current research on obesity consider the Current research on obesity consider the situational factors that leads to overeating, what situational factors that leads to overeating, what cues prompt a person to eat? And how do obese cues prompt a person to eat? And how do obese persons differ in their responses to these cues . persons differ in their responses to these cues .

Factors that influence eatingFactors that influence eating

Responsiveness, to food cues, the sight, aroma and Responsiveness, to food cues, the sight, aroma and taste of food affect how much and when we eat .taste of food affect how much and when we eat .Research suggest that obese people are more Research suggest that obese people are more responsive to such cues (inherited ?).responsive to such cues (inherited ?).Taste appears to be particularly important to obese Taste appears to be particularly important to obese people (ice cream test).people (ice cream test).Obese people are also highly responsive to the sight of Obese people are also highly responsive to the sight of the food (bright light test).the food (bright light test).Overweight individuals often report that their eating is Overweight individuals often report that their eating is increased when they are tense or anxious, in contrast increased when they are tense or anxious, in contrast with normal weight individuals (film viewing). with normal weight individuals (film viewing).

Conscious restraints of eatingConscious restraints of eating

Overweight individuals are more likely to Overweight individuals are more likely to be dieting than normal-weight ones, this is be dieting than normal-weight ones, this is probably the cause of their probably the cause of their responsiveness to food .responsiveness to food .

Research results classify people to Research results classify people to (restrained eaters) and (unrestrained (restrained eaters) and (unrestrained eaters) regardless of their weight .eaters) regardless of their weight .

Exercise and eatingExercise and eating

The level of body energy expenditure is critical The level of body energy expenditure is critical to the weight control .to the weight control .Energy expenditure depends on :Energy expenditure depends on :

- General activity level and exercise .General activity level and exercise .- The basic metabolic rate (the energy needed to The basic metabolic rate (the energy needed to

maintain minimal body functionsmaintain minimal body functionsBasal metabolism accounts for about two thirds Basal metabolism accounts for about two thirds of a normal-weight person’s energy of a normal-weight person’s energy expenditure . expenditure .

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For the overweight ,energy expenditure is inhibited For the overweight ,energy expenditure is inhibited because the metabolic rate is lower in fat tissue than in because the metabolic rate is lower in fat tissue than in lean tissue .lean tissue .Metabolic rate is decreased during food deprivation ,both Metabolic rate is decreased during food deprivation ,both of these factors work against the effort of obese to lose of these factors work against the effort of obese to lose weight.weight.Physical activity accounts for about one third of normal Physical activity accounts for about one third of normal energy expenditure, but it plays more critical role in the energy expenditure, but it plays more critical role in the amount of energy expenditure by an overweight person .amount of energy expenditure by an overweight person .Exercise is critical in weight loss, not only because it Exercise is critical in weight loss, not only because it burns calories, but also because it helps to regulate burns calories, but also because it helps to regulate normal metabolic functioning . normal metabolic functioning .

Behavior modification and weight Behavior modification and weight controlcontrol

Awareness of the individual of the factors that Awareness of the individual of the factors that lead to overeating and trial of changing them lead to overeating and trial of changing them (daily record of eating).(daily record of eating).

Behavior therapy combined with drugs gave best Behavior therapy combined with drugs gave best results .results .

Short-term weight loss is easy ,but the ability to Short-term weight loss is easy ,but the ability to keep weight off permanently depends on keep weight off permanently depends on establishing self-control over eating habits . establishing self-control over eating habits .

In conclusionIn conclusion

Obesity results from the interplay of Obesity results from the interplay of genetic, metabolic, psychological, and genetic, metabolic, psychological, and environmental events , the importance of environmental events , the importance of each varies from individual to individual . each varies from individual to individual .

Despite the complexity of the problem, Despite the complexity of the problem, weight control is possible, in most cases. weight control is possible, in most cases.

THANK YOUTHANK YOU