Hungry for fullness and artificial sugar

Attempts to measure fullness show that it is actually very difficult, particularly if one tries to find a more objective measurement than a person saying "I'm full up".

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Einar Risvik

Senior Scientist
Phone: +47 913 74 880
einar.risvik@nofima.no

We also know that this differs a great deal from person to person, something which is sometimes reflected in weight.

What is hunger?

Hunger – which is the opposite to fullness – is perhaps even more difficult, because mental overrides are even more common, in addition to known physical signals. Fullness or hunger reflects many things: relative fullness of the stomach and intestine and how rapidly blood sugar levels are raised – only to fall again afterward. The length of a meal and variety of what one eats is also significant, so it makes a difference whether all the food is consumed in one portion or in the form of several courses one after another. A meal which goes on for a certain amount of time allows us to gradually realise that we are full – to a much greater extent than if we had eaten it all in three minutes. Variety is also of interest. One might easily imagine that monotony would not stimulate to a large intake of food, but "simple" flavours and foods don’t require much mental attention (unlike the effect of many different stimuli demanding attention and thereby causing fatigue). So the arrow could point either way here and we don’t know which is the more important. It probably varies with the person and the situation.

75 % overweight

There are now very many more people in the world who eat too much than who get too little to eat. This is a frightening trend and the World Health Organisation is warning of a worldwide fat epidemic which will soon affect 1.6 billion people. In the USA, more than 75% of all men over 30 are expected to be overweight within seven years. And the USA is not alone in this – almost all the world’s most populous countries are following the same trend.

We are fooling ourselves

That this is happening is not just the responsibility of the individual, even though the individual must take responsibility for what he puts in his own mouth. It does not appear that knowledge and consciousness are enough to stop this development. I would point to certain trends and ways of fooling ourselves, for which the individual, the food producers and society as a whole must accept varying degrees of responsibility.

Sugar versus starch

A blood sugar level which increases rapidly and then goes down rapidly tends to increase the intake of calories, because of the physiological response which tells the brain "I’m starting to run out of energy – please give me a top up". Carbonated soft drinks have been given much of the blame for increased energy intake, but in principle the blood sugar response to buns is faster and equally short lived. Soft drinks contain normal sugar, consisting of fructose and glucose which together make sucrose. The starch in white flour is only glucose. Fructose must be converted in the liver before we can make use of its energy, whilst glucose goes straight to the blood. We can therefore put a question mark against so called "light" products in which fat and sugar are taken out and replaced with easily digested starch. Even though the energy intake from such a product has been reduced, there is a risk that the rapid rise and fall of blood sugar levels will cause the feeling of hunger to come more quickly than it would otherwise have done. In the worst case this could mean that we eat more calories over a period of time, which is the opposite of what was intended with the individual "light" product. But we don’t know enough about this as yet.

Fat has a good memory

Fibre, fat, protein and "slow" carbohydrates give a feeling of fullness which lasts longer. Fat also gives a high concentration of energy, so fat should not make up too large a proportion of the diet. Sugar and easily digested carbohydrates which raise blood sugar rapidly will, if the body does not have an immediate need for the energy, be converted into fat and stored for later use. At the same time as this is happening, the body puts memory molecules into the fatty tissue, which are there to remind us to eat more if the fat store is taken back out into circulation again. If we come to a situation where the blood sugar level is low, we retrieve our store in the form of fat which is converted into sugar, and which simultaneously sends a signal to the brain to eat more. Slimming is therefore no easy matter, as long as the brain is receiving signals that we could be in trouble if we don’t eat more food.

Later never comes

The concentration of energy in food, how the energy is distributed over time and the physical volume the food takes up all therefore combine to become the key to a more correct diet. Biologically, we are organisms designed to take as much care of energy as possible, so as to have it for later use. Our problem is that there is never any "later", because we have enough food all the time. What we need therefore is food which lasts longer, fills us up more and gives less energy per gram. This is where fibre, water and slow carbohydrates come in: wholemeal flour, fruit and vegetables. Proteins have much of the same functions and provide limited energy, but they can cause constipation if they are ingested in too large amounts as part of the diet.

Sweet looks for sweeter

All the senses work on the contrast intensification principle. This means that the sensory signals will cease if the stimulus continues at the same level. If everything were equally sweet, we would stop perceiving the sweetness. Since people are all born regarding sweetness as positive, we will try to make these signals as strong as possible, so as to get a positive kick all the time. This doesn’t have much to do with our digestive system, but means that a positive sweet taste, for example, becomes a desirable experience in itself. We can see this from cultures which have not been able to afford much unnecessary sugar and where sweets are actually not as sweet. For us sugar is cheap and by using artificial sweeteners which are often 10 to 100 times sweeter than sugar it isn’t difficult to make sweets which are far sweeter than was possible 50 years ago. The theory of contrast intensification tells us that, with a positive stimulus like sugar, we will look for ever more and ever stronger experiences.

Why is an orange so good when you’re out skiing?

This becomes a self-intensifying mechanism. The more sweet things we eat and the sweeter they are, the more we want. This vicious circle is broken if we place ourselves on a lower level of stimulation for a while. In this light the use of synthetic, supersweet substances without energy will drive us towards increasing our sugar intake. Because the stimulation is so powerful, we will naturally also look for greater amounts of sugar to get the same effect on our senses. This also helps to explain why oranges taste so intensely sweet when they are eaten after a tiring ski in the mountains. Your sensory meter has been reset to zero and your tongue is dry. The result is a taste explosion in your head.

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