Biology Forums - Study Force

After a good lunch at 12 pm, I expect not feeling hungry until dinner, but sometimes I feel hungry at 4 pm.  Based on in-take calories from Breakfast, Lunch and Dinner, I should get enough energy from foods for the whole day. 

Does anyone have any suggestions on why I get a feel of hungry at 4 pm?
Thanks in advance for any suggestions

Mechanical Hunger is the easiest to understand, and sometimes to recognize – it’s the feeling of an empty stomach, often accompanied by growling or churning, or a sense of hollowness or tightness in the stomach.

Aesthetic Hunger is the longing for food due to emotional reasons, either you find something that looks appetizing and you want to eat it.

Chemical Hunger refers to the feeling that lies beyond the garden-variety grumbly stomach. It is generally subtle, but if not attended to, can become a deafening roar. It is the sense that “something is missing” or something didn’t quite hit the spot. Perhaps you're feeling shaky or light-headed.

I believe you're experiencing a chemical hunger according to the situation you've described.

Hunger is the physiological drive to eat, influenced by hormones, nutrient levels in the body, and eating patterns. Scientists differentiate this from appetite, which is the psychological drive to eat. I wont discuss appetite here. Scientists also differentiate between hunger and satiety (fullness), because they are regulated by different centres. I will discuss both of these, because they directly affect each other.

The hypothalamus (HT) contains centers that tell you if you're hungry or satiated. Although they are separate centres, the hunger centers inhibit the satiety centers (i.e. when you're hungry you feel less full), and vice versa. When the hunger centers are activated, activity in your sympathetic nervous system decreases, which signals you to eat. The opposite occurs when the satiety centers are activated.

To "decide" which of these centers should be activated, the hypothalamus receives input from a few sources:

• The gastrointestinal (GI) tract (the stomach and intestines)

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Cholecystokinin (CCK) is a hormone released by the small intestine in response to fat entering the small intestine. It decreases activation in the hunger centres of the HT (i.e. it makes you less hungry), and increases activation in the satiety centres (i.e. it makes you feel more full).

Peptide YY is a hormone release by the small and large intestines in response to eating. There is some evidence that protein consumption increases peptide YY release. It also inhibits your hunger centres. Relevance to weight control: Between CCK and Peptide YY, both fat and protein consumption decrease hunger.

Ghrelin is a hormone released by the stomach in response to emptiness. It stimulates the hunger centres in the HT (i.e. makes you feel more hungry). Since an empty stomach causes hunger, you can see how it would be beneficial to slow down the stomach's emptying. The hormones CCK (as mentioned above, it is released in response to fat) and GIP (released from the small intestine in response to food) both delay gastric emptying. Fiber has also been shown to delay gastric emptying. Relevance to wight control: High fiber and high fat meals may help delay the next onset of hunger. Smaller meals also slow gastric emptying, but I'm not sure if it's enough to compensate for the fact that the meal is smaller.

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• From nutrients in the blood

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When glucose enters the the blood stream, the hormone insulin is released. Insulin inhibits the hunger centres of the HT (i.e. it makes you less hungry). Any carbohydrates you eat will enter the blood stream as glucose, however, complex carbohydrates (think whole grain foods) enter the bloodstream more slowly, causing a lower but more sustained level of insulin than simple carbs do (think sugary treats), which will cause a spike and drop in insulin. Relevance to weight control: Complex carbs keep you more satiated than simple carbs.

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• From body fat stores

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Stored body fat releases a hormone called leptin, which tells the HT that you're gaining body fat. If you gain fat (increasing leptin), it decreases your hunger and increases your satiety, and the opposite happens if you lose fat. Relevance to weight control: some people have a disorder in their production or reception of leptin, making it easy to gain weight uncontrollably.
There is also evidence that orexin, a hormone involved in sleep/wakefulness cycles, stimulates hunger. Sleep deprivation has been shown to increase food intake. Relevance to weight control: Get enough sleep.

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At that moment, I don't feel hungry, but feel pain in stomach, so I know I must eat something to release this pain.  would it be chemical hunger in this case?

Does anyone have any suggestions?
Thanks, to everyone very much for any suggestions :>

That's mechanical hunger.

I feel pain in stomach, would the pain caused by stomach acid? if this is mechanical hunger, does anyone have any suggestions on what activate to release stomach acid in afternoon?
Thanks, to everyone very much for any suggestions :>

I don't think it's caused by the release of acid. When food is present in the stomach, peristaltic or wavelike, muscle contractions sweep through the walls of the stomach and help to mix food with gastric juices. However, another kind of intense muscle contraction, called hunger contractions, occur when the stomach has been empty for several hours. Hunger contractions are peristaltic contractions, mainly restricted to the body of the stomach. They can often be particularly strong, resulting in a contraction that lasts for two to three minutes. Hunger contractions are usually most intense in young people, who often have a higher degree of gastrointestinal "muscle tone" than older people. In addition, these contractions are increased by a low level of glucose in the blood, which usually occurs when an individual has not eaten for several hours.

In considering hunger contractions, would be the best to eat every several hours and keep stomach working all days in order to avoid hunger contractions, furthermore, in order to maintain a stable level of glucose in blood, I should keep each meal light and eat every 4 hours.  Foods takes 2 hours to be digested, and let stomach rest for 2 hours before eating anything to make sure enough rest for stomach.  

Breakfast at 8 am
Light Lunch at 12 pm
Afternoon tea at 3:30 pm
Dinner at 7 pm

Do you have any suggestions?
Thanks, to everyone very much for any suggestions :>

To answer your first question, those contractions are not detrimental to your health. If you experience hunger pangs, it's your bodies natural reaction to a lack of food. Similarly, eating too much salt stimulates your thirst. Eating every four hours, as you described is, in fact, the best practice. Generally, however, your body will teach itself when to get hungry based on your biological clock - circadian rhythm.

If I ignore this pain feeling from hunger contractions, and not eat anything. I would like to know on what would happen to my stomach for long term.

Do you have any suggestions?
Thanks, to everyone very much for any suggestions :>

Nothing... Those contractions will eventually weaken due to a lack of energy anyway.

Thanks, to everyone very much for suggestions :>

NP!