Many of us have a sweet tooth. It's hardwired into our brains. Several thousand years ago, when we went long periods of time between meals, we needed to get all the calories we could whenever we had the chance. Sweet and fatty foods are high in calories, so our brains made them taste good to get us to eat them. It was a survival instinct back then that made for fit brains. It doesn't work so well for us now.



Taste Isn't Everything

We've known this for some time. We know that when you eat something sweet you light up pleasure centers, driven by dopamine, in your brain. New research shows it's not just the sweet flavor that pleasures us. We will light up pleasure centers even if we can't taste the sweet foods. The high sugar content of sweet foods cranks up our insulin. It turns out that the insulin spike is enough to activate our pleasure centers.

In a recent study, researchers knocked out the ability of mice to taste sweetness. They proved it by allowing mice to choose between plain water and water spiked with sucralose (a non-digestible sugar with no available calories). Normal mice will prefer the sucrolose water because it's sweet, but these mice couldn't tell the difference. Next, the researchers gave the un-sweetened mice a choice between plain water and sugar water, and they those the sugar water, even though they couldn't taste the difference.

In the same studies, the researchers looked at the pleasure centers in the brains of the mice. Sucralose water (sweet but no calories) had no affect, but sucrose water (regular sugar) cranked up the dopamine in please circuits, whereas in regular mice, both sucrolose and sucrose activate pleasure. This showed that the high calorie content alone was enough to activate pleasure, even in the absence of taste.

Sweet Pleasures, or Not

So what does this mean for us sweet-toothed humans? First, since our pleasure circuitry is similar, it's likely that the same thing happens in our brains (although this remains to be tested directly). Second, we've discussed in the past how high glycemic foods (simple carbohydrate, high sugar) spike your blood sugar and insulin levels. This is likely tickling your pleasure centers and reinforcing high glycemic eating. The problem is that this type of eating is gaining more and more data on increasing your risk for metabolic and cognitive diseases, like diabetes and dementia.

Like anything that stimulates your brain pleasure circuits, it becomes less intense over time. So the more you eat high glycemic foods, the less intensely your pleasure centers are likely to respond. This is also how drug addiction works, and is why people need more of a drug to get the same high over time. Not only that, but when you come off the drug your pleasure centers crash to really low activation and you feel horrible. Similarly, when you try to improve your diet to reduce low glycemic foods you are not getting that pleasure boost so you crave sugar.

Now, to be clear, drugs of abuse and high glycemic foods operate at completely different levels. In the words of Nigel from Spinal Tap, drugs turn your volume up to 11, while high glycemic foods probably crank it up to 3 or 4. But the principle is the same.

It's Never Too Late to Change

The human brain is an amazingly adaptive thing. Even though it's wired to enjoy sweet and fatty foods, we can modify and retrain those brain circuits to adapt to health in today's environment. After all, our brains weren't designed to be pleasured by sweet foods on a daily basis as is the case today.

Fortunately, you can reset your dopamine scale with a focus on low glycemic eating. It takes a week or two of strictly removing excess sugar from your diet, but you can reset the circuits and lose the bulk of your cravings for sweet foods. Furthermore, if you replace the pleasure activating foods with active healthy behaviors that you enjoy, like playing tennis or shooting hoops, you'll have a much greater chance of success.

Reference: de Araujo, Neuron 57 (2008), 930'941.

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