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Lots of us are fat. Why is this?
Obviously, we eat too much. But why do we do this when we know full well it isn’t good for us?
One answer is that in the past we evolved a liking for sweet foods. Before the advent of civilisation we lived as hunter-gatherers. Current thinking is that most of our diet came from the gathering bit – probably about 80%. Gathering nuts and berries is a time-consuming and dangerous activity, so it made sense to concentrate on the most energy rich food and so we evolved our sweet tooth.
Our modern dieting problems result from a deeply ingrained adaptation to a life style that we no longer have. In fact far from having to walk miles to find a rewarding energy source, our modern technology and ways of organising things means that anyone of us can eat just about anything whenever we want to. One of the most convenient foods we have is sugar. It is cheap, easy to store and doesn’t really go off. It also tastes nice and can be combined with lots of other foods generally making them taste nicer. It is little wonder that so many of us have waistlines expanding way beyond what we consider desirable. Sugar isn’t the only culprit, but it is definitely one of the hardest to resist.
Can we use our ingenuity to overcome this problem. Is there a way to fool our sweet tooth? Well it turns out that it is relatively easy to fool our taste sensation. The search for low calorie sugar substitutes started as long ago as the nineteenth century with the invention of saccharin. Saccharin is about three hundred times sweeter than sugar but has no calories. This is a well known product and I am sure we all know what it tastes like. Saccharin isn’t a perfect match for the taste of sugar in tea or coffee, but food scientists understand its properties very well. They are able to produce processed foods and drinks using saccharin that can’t be distinguished from sugar based ones. Very few people can pick out soft drinks using sugar substitutes in blind tastings. So it would appear that there is a readily available technological solution to the problem of putting on too much weight, and we have had it for over a century.
So what are we waiting for?
Unfortunately, it turns out that while it is a fairly simple matter to fool the taste buds on the tongue, fooling the brain is a much tougher proposition. The brain is able to monitor blood sugar levels. Saccharin obviously doesn’t increase blood sugar levels – that being the whole point of using it. So if you eat something containing saccharin you don’t in any way satisfy your hunger. Recent research has shown that the problem is even more deep seated. Guido Frank at the University of Colorado in Denver carried out an interesting experiment. He gave 12 women sweet drinks. One was sweetened with sugar, the other used sucralose – a newish artificial sweetener. The sweetness levels were identical and the women could not tell the two drinks apart.
But when the women’s brains were scanned it was found that the effect on their brains was very different. In particular, sugar triggered off the “reward” sections of the brain much more strongly. The weaker impact of the sucralose worries Frank. He thinks that the weak stimulation to the reward areas might drive you to seek out something to fully stimulate the brain region that has been tweaked. (This is speculation of course; it hasn’t been tested.)
So artificial sweeteners are clearly not the answer to weight loss. They don’t stop you feeling hungry and they don’t fool you brain, even if they do fool your tongue. But do they play any useful role at all? Well they don’t promote tooth decay like sugar does, so if you can get used to the rather odd aftertaste they all seem to have you might keep your teeth in better condition. And they might be useful in helping manage your diet. One of the problems with sugar rich foods is the sheer speed at which you can ingest calories – much faster than your body is able to get the message out that you are full. A diet drink is a better option than a sugar based one most of the time. But a better long term strategy is probably to try and get into the habit of eating unprocessed food without any added sugar and which takes time to chew. There is, after all, nothing wrong with sugar if you deliver it at a pace your body can cope with.
NeuroImage Vol 39 p1559.