There are evolutionary reasons for having a sweet tooth, but why does dessert come at the end of the meal?
Humans, like many other mammals, are born with an innate preference for a sweet taste. This preference can be observed in newborns and even premature babies: the sweet taste helps them relax and suck more, which increases their food intake.
Our mouth contains specialized receptors for the sweet taste. When they recognize a sugar molecule, they turn on a signaling pathway that reaches the brain and provokes a feeling of pleasure. This mechanism is actually an evolutionary remnant from the time when rich and nutritious food was a rare commodity. We prefer sweet taste, since sweet food in nature is usually of good quality – e.g., sweet fruit, which is rich in many nutrients.
It is interesting to observe how the preference for sweet taste declines with age, as children prefer sweet taste more than adults do. One of the explanations for this phenomenon is that children require very rich food as long as they are growing, and this need diminishes later on.
Small children learn what the "right" taste of food is as they become exposed to different foods. Research shows that children who became accustomed to sweetened and processed foods will also prefer to consume sweeter food as adults. Namely, the level of sweetness that they would define as "tasty" is high. Therefore, they would prefer to consume large amounts of sugar, which may lead to obesity and other syndromes. Other studies have found that the more fruit children consume, the more they will prefer a lower level of sweetness, since they learn that the appropriate level of sweetness is that of fruit, and not of processed and sweetened food.
Biology explains why we prefer sweet food, but it does not do a good job in explaining why people have a craving for a sweet dessert at the end of hearty meal. We put an effort in finding a plausible scientific explanation, or at least one that will relieve our guilt. However, the answer is that there is probably no biological mechanism behind this craving, and it is just a force of habit.
This claim is reinforced by the fact that some cultures do not have the habit of ending a meal with something sweet – for instance, in France, where they usually end a meal with ripe cheeses, or in different regions of India, where there is no dessert at all. If it were a biological need, it would most likely be a cross-cultural custom, like the global reaction of babies to sweet taste. Dessert may have come from an attempt to "bribe" children into eating their meat and broccoli, which lead to the habit of ending a meal with something sweet.
In any case, as far as we know, dessert does not have a hormonal or metabolic excuse, and it is just a habit – a behavior we adopted over the years, influenced by the customs of the culture we live in. So the only way to overcome that craving is using will power. Stay strong!
Translated by Elee Shimshoni