Why Do We Need Food When We Are Hungry?

By Dr Harold Gunatillake - Health Writer

We all love food whether we are in  hunger mode or not. Have you ever thought what mechanism works in the body to make you feel hungry?
Michael Lowe, a professor of psychology at Drexel University in Philadelphia says this about hunger. “Feeling hungry can mean at least two things and they are pretty different”.

There is the traditional concept of hunger when you haven’t eaten for a couple of hours, and you would feel and complain that you are hungry. Children cry and get irritable when they get the traditional hunger pangs. Your stomach starts rumbling and you find it difficult to concentrate on what you are doing as the urge for food becomes a priority.

Professor Lowe says,” This feeling of hunger stems from your body’s need for calories; the need for energy prompts the signal that it’s time to eat”.
This hunger is referred to as ‘Homeostatic hunger’. “It is driven by a series of signals originating in the brain to tell us we need food for fuel,” said Dr. Amy Rothberg, Director of the Weight Management Clinic and an Assistant Professor of Internal Medicine in the University of Michigan Health System’s Division of Metabolism.

We need approximately 1,200 calories to run all the machinery in the body and for basic activities like talking, walking, sleeping and so on. The rest of calories from food another 800 cals are used for your daily activities.

Hormones in the body send signals to the brain when you are hungry. The most important hormone is called ghrelin- also referred as “hunger hormone” start rising in the blood stream to signal the brain. It is released primarily in the stomach and is thought to signal hunger to the brain. Immediately you start eating, the brain suppresses the release of this hormone. This is due to certain satiety responses which signal fullness in your belly which tells the brain that ‘we are getting enough food’. When you are done with the consumption of food, another set of opposing signals take place. They are hunger-stimulating peptides called oreigenic hormones and hunger-suppressing anorexigenic hormones.

Dr Amy Rothberg said these hormones are responsible for telling the brain that a person needs to eat or that a person feels full.

One should eat nutritious food – a balanced diet with carbs, fats and proteins with a dessert of fruits to feel full and satisfied.

A diet containing fibre and lean protein keeps you feeling full more than eating processed starchy foods. For example, white rice, a staple diet among Sri Lankans gets digested and absorbed fast making you hungry quite fast. Eating unprocessed red or brown rice keeps you full much longer. Sri Lankans are fortunate that there are many local high fibre fruits like jak, Kohila roots, many varieties of yams and high fibre fruits to feel full for a long time without feeling hungry.Rothberg says that protein diet is the most filling of the macronutrients. Eat an egg in the morning for breakfast you could wait without being hungry till mid-day.

Artificial sweeteners

You should be careful of these zero calorie foods like the artificial sweeteners. They can confuse the brain with fullness signals to signify that you have not eaten enough when you have and the brain may secrete hormones for you to eat more. As a consequence taking non-calorie sweeteners make you more over-weight rather than slimming.

People wanting to lose weight should avoid artificial sweeteners for the same reason.

The gut microbes don’t seem to like artificial sweeteners either. They seem to convert these sweeteners into sugar in the gut and make the situation worse. Ruthberg pointed out that these sweeteners may impact feelings of hunger and fullness. Other than the homeostatic hunger so far discussed, we have another type called hedonic hunger. In this type of hunger, there food cravings and the feeling of wanting to eat. Lowe published in the journal Physiology & Behaviour that the term ‘hedonic hunger’ was coined in 2007. He said that the most widely accepted theory was the human predisposition to high palatable foods.

Today, most people don’t cook at home, but prefer to relax in the restaurant and have a palatable meal with plenty of sugar and salt. Hunger is not the important element here. Lowe said that people want to eat even when they don’t need to. Hunger and hormonal signals are not priorities in hedonic hunger. Hunger may come due to the smell and the visual display, probably after a glass of red wine, company and the ambience. It is more seeking pleasurable time rather than hunger need.

The need for calories for metabolic processes come from hunger signals as described earlier. In hedonic hunger it is the pleasure that attracts the palatable food.

A good example as Lowe puts it, ‘A person who hasn’t eaten in 12 or more hours is experiencing homeostatic hunger, whereas a person who wants dessert after finishing a filling meal is experiencing hedonic hunger’. Hedonic hunger is addictive in certain societies. People must for health reasons avoid highly palatable tempting foods out of the house, said Lowe. Hedonic hunger is harmful, subjected to obesity, heart disease, high blood pressure and so on.

Role of Leptins

Functions and need of ghrelin has been discussed briefly above. Leptin, another hormone secreted by fat cells, is a mediator of long-term regulation of energy balance by suppressing food intake. As mentioned earlier, ghrelin in comparison is a fast-acting hormone functioning as a role in meal initiation and increasing one’s appetite.

Both hormones participate in energy or calorie balance. For obese people, the level of leptin seems to be increased whereas ghrelin hormone secretion is decreased. Leptin though it  functions as a food suppressant, is resistant in obese subjects. It is possible that abnormalities in the leptin and ghrelin systems may be contributing to the development of obesity among people.

In children having anorexia nervosa, ghrelin levels seem to be high and decreased than in obese children.

The appetite suppressant leptin is much less secreted in thin people and high in fat people as mentioned previously.

In conclusion, when the body needs food hunger pangs are brought about by signals from the brain and ghrelin seems to be released by the stomach lining. The moment you initiate eating leptin an appetite suppressant would be secreted by the fat cells. A balance in secretion of both hormones governs the energy levels and weight control.

Sorry, leptin is not marketed as a supplement to solve our obesity problem globally.

Some reference to: ‘The Science of Hunger: How to Control It and Fight Cravings’ by Sara G. Miller, Staff Writer

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