UNDERSTANDING HUNGER AND SATIETY

Hungry? The question "why do we feel hungry?".The answer : It is because we need to get nutrients to survive. Hunger is the motivation for us to be able to know that we need to get the nutrients in our body. But how do we really know that we are hungry? The answer can be analyzed by three different components: biological, learned, and cognitive.

Fatty acid theory states that our bodies have receptors that detect an increase in the level of fatty acid. Activation of the receptor for fatty acid triggers hunger. Heat-Production theory suggested by Brobeck (1994) states that we feel hungry when our body temperature drops, and when it rises, the hunger decreases. This might at best explain that we tend to eat more during winter.

Unlike any other beings, we humans use an external clock in our daily routine, including when to sleep and when to eat. This external time triggers our hunger. For instance, when the clock says 12 pm, lunch time, many people feel hungry just because it is lunch time. This hunger is triggered by learned behavior. In addition, the smell, taste, or texture of food also triggers hunger. For instance, if you like french fries, the smell of frying potatoes may trigger your hunger. However, this preference of taste, smell, or texture is a culturally learned preference. For example, an often heard expression is "I am hungry for something sweet." People keep feeling hungry until these four tastes are satisfied. : sweet, sour, bitter, and salty.

Colors also contribute to hunger (red, green and not blue). Blue is said to be an appetite suppressant.

Many people eat foods based on their ‘perceived knowledge of what foods are good’ for them. For example, if you have conditioned yourself that low fat, low sugar, and low sodium food are 'good', then you will learn to change your preference and want to eat "good food" only .

Hunger - one of your body's strongest and most beneficial stimuli - helps insure that you consume enough Calories for your needs. However, it also works against you when you're trying to lose weight. You could easily lose weight just by eating less, but the less that you eat or the longer you postpone eating, the hungrier you become, and the longer it takes your hunger to subside once you do begin to eat. So the hungrier you are, the more likely it is that you'll overeat, consuming extra Calories that can quickly slow or reverse your weight loss.

Satiety

The mechanism of hunger and satiety are not necessarily the same. There are two mechanisms for satiety. One is at the brain level, the other is at the gastrointestinal tract level. There are two places in the hypothalamus,( Ventromedial Nuclei gives a signal when to stop eating, and the Lateral hypothalamus gives a signal to start eating) part of the brain, that controls hunger and eating. We feel satiety at the brain level because of the function of the Ventromedial Nuclei. At the level of the gastrointestinal tract, satiety signals come from the stomach, which controls short-term eating.

As you know, the only way to end hunger is to eat. Eating provides satiety - a pleasant feeling of fullness and the corresponding reduction of hunger. But did you also know that some foods are better than others for satisfying your hunger? A baked potato, for example, will probably "fill you up" much better than a serving of candy that has the same number of Calories.

Studies by Australian researcher Dr. Susanna Holt (University of Sydney) have lead to the development of one of the most exciting diet concepts ever, called the "Satiety Index".

After two hours of eating a 240 cals portions of a variety of foods the volunteers were questioned about their hunger to see if their subjective impression of satisfaction matched their eating behavior during the second go at eating (after a few hours). Using white bread as the baseline of 100, 38 different foods were ranked. ( foods scoring higher than 100- more satisfying than white bread)

What Really Satisfies?

Holt found that some foods, like croissants, are only half as satisfying as white bread, while boiled potatoes are more than three times as satisfying, easily the most satisfying food tested.

The more fiber, protein and water a food contains, the longer it will satisfy. Another thing that makes a food satisfying is its sheer bulk. "You can eat an awful lot of popcorn without taking in a lot of calories," says Holt. "It may not weigh much, but it makes your stomach feel full just because it takes up so much space. Oranges come out very high on the index for the same reason—but orange juice probably wouldn't, even though it has the same number of calories."

As a group, fruits ranked at the top with a satiety index 1.7 times more satisfying, on average, than white bread.

“This type of information can have important implications for those wanting to lose weight. Muesli is only half as satisfying as porridge [oatmeal]," Dr.Holt adds

Some Surprises

In general, the more satisfying a food felt, the more effective it proved as a nibbling deterrent. But even here there were some surprises.

"Fatty foods are not satisfying, even though people expected them to be," says Holt. "We think the reason is that fat is seen by the body as a fuel which should be used only in emergencies—it stores it in the cells instead of breaking it down for immediate use. Because it doesn't recognize the fat as energy for immediate use, the body does not tell the brain to cut hunger signals, so we go on wanting more. Carbohydrates are the opposite—they raise blood glucose so the body knows it has gotten enough fuel."

Overall, the carbohydrates deter nibbling best, while protein-rich foods such as cheese, eggs, baked beans, meat and fish come second, and fruit third.

Experiments with Satiety

For years, researchers have studied satiety. While many things are known to influence satiety - including individual differences in endocrine levels from one person to another - one of the biggest factors is the type of food that you eat. Some foods fill your stomach faster and/or remain in your stomach longer, and therefore do a better job of holding off hunger.

The results of Holt's study, indicate that satiety is most strongly related to the weight of the food consumed. In other words, the foods that weigh the most, satisfy our hunger best, regardless of the number of Calories they contain. However, higher amounts of certain nutrients, such as protein and dietary fiber, also appear to improve satiety. Some examples of more filling per calorie comes, in decreasing order, are watermelon, carrots, oranges, fish, chicken, apples, oatmeal, popcorn, yogurt, banana, cheese, brown rice, white rice, peanuts, ice-cream, white-bread, sugar and butter.

The degree to which a food is satiating largely depends its compositional makeup rather than its nutritional value -- although highly satiating foods also tend to be highly nutritious. Satiety, or the physical sensation of fullness, is generally short-lived after eating refined food products or foods rich in simple sugars. Although a food’s capacity to satisfy is typically the result of a combination of characteristics, most highly satiating foods have one trait in common -- they’re rich in fiber.

The importance of such studies is to understand hunger, and find out if there is a way of predicting satiety; If YES, we would be able to select foods that satisfied our hunger, but contained fewer Calories. Such applications come handy in the field of obesity and weight loss. ( Eat ‘more’ –Lose weight…. ‘more’ because you are ‘satisfied’ faster while the calorie intake is lesser.). Cabbage soup is a classic example of this.

A Few Words of Advice

Holt warns of some confusion in the interpretation of her study's findings. "The Satiety Index scores reflect the total amount of fullness produced by the portions of the test foods over two hours—i.e. short-term satiety.” Holt notes.

"In the case of fruits, fullness dropped off quickly towards the end of the second hour, reflecting the rapid rate of gastric emptying." she adds. 'Roughly speaking, the more fibre, protein and water a food contains, the longer it will satisfy.

"Many 'health-conscious' dieters," she continues, "will eat a meal based on several pieces of fruit and some rice cakes and then wonder why they feel ravenous a few hours later. These kinds of extremely low-fat, high-carb meals do not keep hunger at bay because they are not based on slowly-digested carbs and probably don't contain enough protein."

General Observations

Foods that contain large amounts of fat, sugar, and/or starch have low Fullness Factors, (another identical index) and are much easier to overeat. Foods that contain large amounts of water, dietary fiber, and/or protein have the highest Fullness Factors (FF). These foods, which include most vegetables, fruits, and lean meats, do a better job of satisfying your hunger. Most liquid foods will have above average Fullness Factors, due to their high water content. Liquid foods do, in fact, have a relatively high satiating effect, at least for the short term

There are, however, other things that can influence a food's ability to satisfy our hunger. In particular, a food's specific taste and texture - i.e. its palatability - can encourage or discourage consumption. Palatability of a food is a highly individual and subjective value, though, that can't be accurately measured. Main criticism of FF is that the index is derived from a small data set and that too based on subjectively reported, rather than directly measured, criteria. But that is the hazard of the game.

Investigation of satiety indices of foods is considered an interesting area of future research, which, if validated, may aid in the selection of appropriate foods to promote energy balance.

A more established index is the GI which when coupled with satiety index can be used to classify foods based on their blood glucose raising potential and

how fast ‘you feel you are full'.

EATING TO SATISFY HUNGER IS COMPLICATED…..

3 Replies

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  • must read article for diabetics

  • It is complicated, especially when you realise people have a vested interest. Eating potatoes may satisfy your appetite in the short term, but in a couple of hours time?

    I find that meat, with fat, tends to stop me being hungry. It turns off my appetite within a short time (you don't have to wait the twenty minutes for your stomach to feel full that some experts refer to), and you don't get hungry for hours either. However, I have noticed I can feel not hungry but still lack the energy for doing activities if I cut back too far with the carbs. Eating low GI is always preferable to high GI. If you have to top up with high GI because of hypos, something is wrong!

  • Sorry, I should have mentioned this....

    The mention of potatoes was in the context of nutrition and satiety and NOTin the context of diabetes.

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