Dear Mark: Your Brain on Junk Food

Clearly, we eat not just to fill our stomachs but to satisfy a whole host of biochemical drives. The brain is built to incentivize our efforts not just with the quieting of hunger pangs but the kick-starting of an intricate hormonal “reward” system. When it comes to diet, I’ve always said what nurtures the body nurtures the brain. The proof is in the biochemical picture. And while I wholeheartedly believe that we each choose what we eat and how we treat our bodies, there’s something to the science that shows addictive properties in junk food. I occasionally get emails on this topic. Here’s a timely one from last week.

Dear Mark,

I’m wondering if you believe in junk food addiction. I’m very new to the Primal Blueprint diet and have been having some serious issues. I feel like it’s one step forward two steps back some days. For instance, I fell off the wagon entirely at Halloween, thinking a few pieces from my kids’ stash wouldn’t be a big deal for a couple days. But a few pieces turned into a whole backslide. I found myself roaming the house for days afterward craving foods I thought I was done with.  I’m finally getting back on track now, but I’ll admit I’m a little stunned. I don’t want to make excuses for myself (no one made me eat the stuff to begin with), but is there something more complicated here than I think?

I know there are those in this community who consider themselves recovering sugar addicts, so to speak. Some regularly offer their comments on the boards/forum threads, and others have written me personally about the difficulty of breaking through this first “wall” on the way to going Primal. When you’re addicted to sugar (or carbs in general), even a day’s break can make you feel like a rabid fiend scouring for your next fix. Cutting all grains in addition to sugar (since grains readily convert to glucose) will be critical for your success in this case. In fact, you probably can’t eliminate a long-term sweet-toothed sugar craving without eliminating grains.

An interesting study presented at the Society for Neuroscience conference last month gets closer to the biochemical reason for this. As researchers observed rats that were fed a steady diet of “junk food,” (chocolate, cheesecake, bacon, sausage, etc.) they found that the “’animals’ brain reward circuits became less responsive’” over time. Not surprisingly, the animals began to exhibit “compulsive overeating habits.” Even when subjected to mild shocks, the animals were undeterred as they chowed down on the junk food, and they refused to eat healthier food when it was the only feed available. In essence, the junk food dulled their pleasure centers. As a result, they kept seeking out the junk food and eating in an attempt to trip the reward trigger, but the blunted neurological response was never enough. This diminishing of pleasure center response, the researchers added (PDF), paralleled what they have witnessed in rats “’as they become addicted to cocaine or heroin.’” (Comforting, eh?)

Other studies have shown similar findings. Using human brain imaging, researchers have found lower dopamine (linked to reward and pleasure response) receptor levels in obese people compared to subjects in their recommended weight range.

By the same token, restricting food appears to increase dopamine receptor levels (through gene expression, of course). Mice whose food intake was limited showed higher dopamine D2 receptor levels than mice that were allowed to eat all they wanted. The better reward response your brain has, the more sensitive it is to pleasure. Consequently, you feel pleasure and motivation from lower intake of food or other rewards, and perhaps you simply learn to derive more pleasure from eating healthy foods – the foods your genes expect you to eat. If your response is dulled over time through junk food or overeating, it will take more to trip the pleasure response. This pattern clearly impacts more than weight; it’s one of long-term mental well-being and overall happiness.

On a side note, let me grouse and grumble for a minute about the terminology used in this and similar studies. The diet fed to these animals, as I mentioned, included chocolate, cheesecake and bacon. This, the authors exclusively label a “high fat diet” as if that’s the only defining feature of it. Unfortunately, this is standard operating procedure in these studies. The headlines and media summaries run with this “high fat” premise, and the vast majority of the unknowing public eats up the distortion (pardon the pun).

But back to the original issue: how to get the junk food monkey off your back. Early backsliding, as our good reader described, isn’t uncommon, and it definitely isn’t reason to get discouraged. The worse your diet was before, the more time and commitment it will take to make all the changes (actually, all the gene reprogramming) and, moreover, make them stick. You’ll be undoing both behavioral and biochemical patterns. Your body can and will regain homeostasis, and your hormones and neurotransmitters will recalibrate themselves.

The best thing you can do to make the transition easier on yourself is to stick to your guns when it comes to diet (possibly why some people find it easier to give up sugar/grain carbs cold turkey) and take top-notch care of yourself otherwise. It can be tempting to tackle one thing at a time in taking on a Primal lifestyle (e.g. first the diet, then add exercise, then go to bed earlier for more sleep and finally work on decreasing stress). If you’re really having trouble getting over the sugar/carb hump, that kind of pure sequential approach might not be the best choice for you. In truth, all the lifestyle elements influence physiological balance. Think about improving your lifestyle on other fronts first and/or while you simultaneously switch over your diet. Exercise, in particular, has been shown to both encourage dopamine release and increase dopamine receptors. Of course, it’s important to do the right types and amounts.

Finally, once you’ve hit your groove, I’d suggest staying the course. You might think a short-term break from the Primal diet might not have an impact, but for some people (especially early on in the transition) even a brief interlude (e.g. holiday weekend) is enough to derail the train. As much as we do talk about the 80/20 Rule, try to keep your eating as Primal as possible during this time. Resist momentary temptation, and you might save yourself a week’s worth of efforts regaining lost ground. Keep Primal snacks handy to get you through moments of temptation. Maybe have an extra piece of turkey rather than dessert!

Thanks, everybody, for your questions and comments. Let me know what you think about this week’s Dear Mark, and keep those questions coming!

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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