Have you ever gotten a serious case of the munchies before? Chances are we all have, especially if we’ve been eating from bags of low-calorie labelled sweets. So why do we continue to feel hungry after eating these supposedly healthier snacks? The answer lies in the type of sweetener used in these foods—whether it's real or artificial sugar. While your taste buds probably can't tell the difference between the two, your brain certainly can.
An ancestral sweet tooth
Our fondness for sweet tasting food comes from an evolutionary standpoint. Primitively speaking, sugar is often associated with energy-rich foods such as fruits and vegetables. While artificial sweeteners act as a sugar alternative, they don't provide the calories and energy that evolution has taught the brain to associate with sweetness. Although it's been known that our brains can distinguish between real and artificial sugars, the mechanism behind it remained a mystery until a recent breakthrough.
In a new study, researchers monitored the brain activity of fruit flies when they were presented with both non-nutritive sugar and real sugar. As the fruit flies licked the real sugar, it activated a cluster of six neurons that triggered the release of a hormone. This hormone had receptors in the gut and brain and aided in the digestion process, thereby encouraging the fruit flies to continue eating the nutritious sugar.
However, when the fruit flies licked the dietary sugar, the same hormone and digestion reaction were not observed since the zero-calorie sweetener didn't provide energy or any nutritional value. In the end, the fruit flies chose the real sugar over the artificial one as they required the energy and calories of the real sugar.
Do humans experience the same sugar-coated distinction?
Since the molecular processes observed in the brains and guts of fruit flies are also present in humans, researchers believe that we share the same sugar differentiation abilities. If this was the case, then it would help explain why dietary foods don’t often satisfy our hunger. As the hormone and digestion processes aren’t activated by artificial sweeteners, we continue to feel hungry even as we continue to eat.
Picture it like this: if you were to eat an entire box of low-calorie ice cream bars, your brain wouldn’t recognize the artificial sugars within the ice cream and therefore your body would still feel hungry. Your food craving would likely last until you started snacking on something that had enough calories to meet your energy demand.
Researchers believe that the sugar-activated neurons observed in fruit flies can be found in roughly the same area within human brains, giving a specific location for future studies. These six neurons need to be triggered by real sugar in order to generate a response that controls the feeling of hunger, and consequently the amount of snacks that we end up eating.
So although our taste buds can be fooled when it comes to consuming artificial sweeteners, the brain is ultimately the best sugar detector of them all.