Obesity, drug addiction, and dopamine

Eating junk-food can be addictive, and apparently, it causes brain changes that look eerily similar to drug addiction. That’s the message not only from the rapidly fattening waistlines of Americans everywhere, but also from the Johnson and Kenny labs at the Scripps Institute.

Food and drug addiction

The idea that obesity is caused by a compulsive pattern of eating, and that there could be a similarity between such compulsive eating and drug addiction isn’t super new. In fact, Dr. Volkow from NIDA seemed to make research into this association her goal when taking  the helm of the addiction research kingdom.

When you think about it, the notion isn’t far-fetched: Drug addicts continue to take drugs, in increasing amounts, even though they’d often like to stop (at some point) and in the face of negative consequences and the common loss of other important life functions (like family, work, etc.). Obese individuals are quite the same, eating more and more food regardless of their desire to adopt a healthier diet and in-spite of ridicule, low self-esteem, and decreased functioning that often accompanies extreme weight gain.

The research by Johnson and Kenny examined whether exposure to the kind of high-fat, super high-calorie foods that floods the junk-food market are responsible for creating food-addicts in a similar way to drugs that alter the brain in ways that make stopping more difficult.

Dopamine, reward, and junk-food

The study took three groups of rats and gave them either the regular chow diet lab animals are used to or the worse kind of birthday party food: bacon, sausage, cheesecake, pound cake, frosting and chocolate. You can imagine the party going on in the rat cages that got to eat that! Of the two groups that got to eat the crazy-fat food, one had unlimited access while the other got to binge for only one hour a day.

The bottom line: Only the rats that got unlimited access to the fat-party food developed compulsive eating habits that resulted in roughly twice the weight gain of the other two groups and the ability to continue eating even in the face of signals for punishment (a light that they were trained to associate with shocks).

When the researchers looked deeper, they found that the brains of these rats suffered a significant reduction in the density of a specific kind of dopamine receptor (D2) in a brain part known as the striatum, the same kind of reduction common in drug addicted people and obese individuals. This receptor type is often thought to be important for regulation of impulses, both physical and otherwise. It therefore makes sense that losing this type of function would cause uncontrollable eating or drug taking.

Are drug- and food-addictions the same?

While this research isn’t saying that compulsive eating, or obesity, are the same as drug addiction, it does strongly suggest that there are common mechanisms in both. More importantly, it reveals a common process that unfolds when over-exposure to the reward, in this case food, occurs. This tells us that there can likely be common pathways to these different addictive disorders, though whether any specific person ended up a food- or drug-addict because of this kind of process is still an open question. I wonder if we’ll see something like this with sex addiction soon…

Citation:

Johnson and Kenny (2010) Dopamine D2 receptors in addiction-like reward dysfunction and compulsive eating in obese rats. Nature neuroscience, 13, 635-641.

Give me SUGAR!!!! And a little food addiction on the side…

sugarSo while we’re sitting here talking about drug addiction, quite a bit of research in the last few years has looked into food, and specifically high-sugar-content foods, as a possibly addictive substance (food addiction).

The focus started when the new head of NIDA (The National Institute on Drug Abuse), Dr. Nora Volkow, who’s been doing research on obesity, took her seat a few years back. Since then, there have been quite a few papers showing that when given foods (or water) high in sugar content, animals develop behavioral patterns that are very similar to drug addiction.

This makes sense from an evolutionary stand point, since sugar gives our bodies carbs, which supply energy for our daily activities. However, it’s probably no secret that 50,000 (or even 1000) years ago, people weren’t consuming foods with refined sugars crammed into them (refined sugars have only been around for about 250 years). Back then, people needed all the energy they could get their hands on.

Unfortunately for us, evolution doesn’t move as quickly as our industrial and technological advances, which means we now get more of the high energy foods more easily, all while moving less and therefore putting out less energy.

The result? Atkins diets and the likes recommending low carb intake, which in actuality, should probably read “sufficient carb intake.”

A very recent paper has shown that even artificial sweeteners (specifically saccharin, see citation), may be able to induce these types of behaviors. In fact, saccharin sweetened water (and also sugar sweetened water) was chosen over cocaine, even for animals that already liked cocaine, and even when they were offered more and more cocaine!!! How’s that for amazing?!

What does this mean for food addiction?

Well for one thing, it means that if we want to battle the obesity problem in this country, we need to re-examine the availability of these high-sugar, high-calorie foods. But, it may also mean that low calorie foods that are artificially sweetened may soon be shown to be as bad for us…

I’m telling you, by the end of all of this, we’ll learn that growing your own vegetables and fruits is the only way to stay healthy. Come to think of it, even then, I know at least one person who may be addicted to fruits…

Question of the day:
Does your experience with high-sugar foods lead you to agree or disagree with these research findings???

Citation:
Magalie Lenoir., Fuschia Serre., Lauriane Cantin, Serge H. Ahmed (2007). Intense Sweetness Surpasses Cocaine Reward. PLoS ONE 2(8): e698.