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Why We Eat: Cravings

Last week I picked up the theme of hunger [1] with an intention to visit all the angles of the instinct – the physiology behind it first – but also the outer reaches of hunger’s emotional and social sway. The fact is, I can’t think of an instinct (other than sex [2]) that influences our evolution more or perhaps a more complex motivation. It’s one of those areas in which you can’t always separate biology from emotion. (The more you learn about the human animal, I think, the more apparent the melding of these two fields/forces becomes.) Enter cravings. Beyond the general experience of hunger (Feed me now!) are the urges toward particular foods (Need THIS now!). What exactly goes on here? What’s the real impetus behind our cravings, and what’s the ultimate pushback we can offer on the way to derailment?

For many, cravings bring to mind the proverbial pregnancy [3] tales. Back in the day, my wife and her friends would compare their pregnancy cravings with as much laughter as zeal. One woman knew she was pregnant each time simply by the ravenous craving for a hamburger from a certain restaurant. “I’ve never felt such an insistent pull toward a specific food,” she explained at dinner one night. “Come hell or high water, I was going to get my hands on that burger if it was the last thing I did.” Another friend went through several clementines a day for her entire second trimester. The cravings ran the gamut from steak to spices. (An interesting trend that beef [4]was such a common hit, I always thought…)

Common thinking for years allowed for the idea that cravings in some cases were responses to nutritional deficiencies [5] however subtle or dramatic. The tide seems to have shifted with most experts and studies pointing more or less exclusively to psychological and social influence. While it may not be popular opinion, I’ll admit I still leave room for the role of nutritional need as something of a factor at least in certain cases, pregnancy being one. Maybe I’m just taken in by the gratifying sight of someone enjoying a fabulous steak – its hefty iron dose [6] aside. I do wonder, however, if those who eat a poor diet [7] are inclined to eat more because the body knows it’s still lacking. Unfortunately, the research doesn’t drive down that road far enough at this point.

An aside… On the extreme side of craving, we see the instance of pica, in which people (particularly pregnant women) crave non-food items. While clearly there’s not much evolutionary sense in eating some of the odd items people do today who have pica (many of them things Grok [8] and his kin had never heard of), the dirt and clay craving [9] may not be as insane as we moderns would assume.

All this said, I think by far our experience of cravings today have to do with the power of suggestion (e.g. marketing influences) [10] and the chemical reward that comes with certain foods. (Ah, the power of glucose [11]…) Let’s home in on that element of craving for today.

Research has shown time and again (including MRI imaging) that the brain areas activated by cravings [12] are the same as those implicated with drug and alcohol addiction, including the hippocampus, caudate and insula – areas that collectively tap into our memory of experience, the reward system that gives us our anticipated pleasure and the emotional association we’ll carry forward about that food (PDF [13]).

It becomes a process of continual reinforcement (if/when we participate) [14] as people eat what they crave, which again elicits the reward and further imbeds that reward for eating a particular food (PDF [15]). We eat the food, and our reward circuits are going haywire all while our cognitive control mechanisms become dampened. As with alcohol [16] and drugs, the more we eat these foods, the more the hormone receptors responsible for that rewarding sensation can become dulled. Our response? We eat more of the same/similar food [17]to get the same reward.

While we all have our favorite foods (the result of complex memory, cultural habituation and emotional association), sugar and other high carbohydrate content food act most readily on the brain. Sugar has been likened to cocaine, and research has observed [18] its associated neurochemical changes and the eerily matching patterns of bingeing [19], withdrawal, craving and cross-desensitization.

The biological fact is, we’re playing with the same fire and neuronal circuitry, and – for some of us – fighting a similarly rough battle to wrestle free of the hormonal circus [20] (or – it’s not an overstatement for some people – hell) that takes over.

When we acknowledge the power of cravings, it’s natural to ask what our best defenses are in these situations. While our brains’ reward systems generally work the same, our responses (and perhaps even sensitivity) to cravings differ widely. I think it’s useful to consider what triggers us [21] to begin with. Can we cut off a craving at the pass and spare ourselves an internal battle?

Research suggests all manner of strategies that seeks to manipulate our environments and exposures. When study subjects worked at an organized desk, they were more likely to make a healthy food choice at the end of the research session compared to those who worked in a cluttered environment (PDF [22]). On the other hand, while an orderly space might encourage healthier eating overall, a seeming opposite input might help us fend off a craving once it sets in. One study shows that bombarding ourselves with visual stimuli [23] can co-opt our brain’s bandwidth, so to speak, and reduce the mental fixation. Some research shows we shouldn’t overtax our capacity for self-control [24] in a day even though other studies suggest self-discipline is a muscle we need to build and can continually strengthen. (I think there’s truth in both camps.) Likewise, we can apparently use a non-food smell like jasmine [25] to “compete” for the brain’s attention and divert it from food cravings. On a simpler note, exercise, research also shows, can dull our brain’s reaction [26]to food images.

Beyond the tricks, of course, are the common sense and maybe more holistic approaches to addressing cravings. Since I know exercise can offer its own endorphin [27] hit, I can work out when I know I’m feeling an emotional slump [28] or am tempted more than usual by triggering foods. Likewise, because I know sleep deprivation [29] and stress skew hormones related to hunger and cravings, I can give my body the quantity and quality of sleep it needs [30], minimize exposure to stressful situations and foster emotional and physical resilience [31] in myself. The better we take care of ourselves in general (and I don’t just mean the better we discipline and push ourselves to perform all the “shoulds”: I should eat Primally, I should exercise and move each day, I should go to bed at 10:00, etc.), I think the less vulnerable we are to the lowest common denominator of personal rewards. It’s about filling our broader needs.

When we’re stressed or agitated or feel “hooked” by the thought of a food that isn’t a reasonable response to legitimate hunger, it’s a smart thing to ask, “What do I need to do to take care of myself right now?”. Maybe my answer to that question is to get up from my desk and go for a walk. Maybe it’s to call a friend or family member. Maybe it’s to take a nap or spend some time pursuing a leisure activity [32] instead of work [33].

Along a similar vein, research shows that mindfulness [34] practice can help us “stay” with the uncomfortable feelings that often urge us to eat – particularly to eat those foods that trip our reward circuits in powerful ways. While research shows that mindful eating can help binge eaters, for example, view their taste preferences with more compassion and reduce binge behavior [35], mindfulness has also been studied as a way to resist cravings by those with substance abuse issues. Sarah Bowen, a University of Washington researcher, has developed a program called Mindfulness-Based Relapse Prevention (MBRP) [36], which showed better long term results than conventional treatment models. The method teaches people to become “aware” of the emotional and physical sensations of craving, meet the experience “with compassion” and then learn to “tolerate craving and negative emotion” that commonly triggers substance use. She stresses that the underlying power of mindfulness is applicable to anyone because she views substance abuse as “another example of that too-human automatic drive to move toward pleasure and away from pain.” Applying mindfulness modality to substance abuse, she says, helps people “disengage from” the “automatic” behavior.

Given that food is an abused substance for so many people (whether occasionally or chronically/clinically), can mindfulness offer the most effective response to food craving? Can it tap into a sense of choice and responsibility in ways that make healthier eating behavior more realistic for some people? My feeling is yes, and other research (PDF [37]) appears to suggest [38] as much. Not only does it address underlying tendencies, but it jibes with common human behavior. It makes Primal sense. Getting real about how the human mind operates and learning to harness those innate tendencies can be considerably more effective than denying them (akin to that carnival game in which you’re always trying to smack down the spring loaded pieces that keep popping up from the many holes).

In the end, the best approach to behavior change is usually a combination of factors. Why not change our environments and exposures when we can? Do we really need to invite ourselves to temptation when we can sidestep the incidence altogether some days? Taking care of ourselves should be on the daily docket anyway, right? If we’re not doing it already, why the heck not? The fact is, the more responsibility I take [39] for my life and health, the more I realize how much time and commitment I need to make to myself. (I have the choice to bristle against it if I so desire, but no good that comes of that grievance. I have to drop the righteousness and anxiety about not having time for myself.  With time and practice, you learn to make yourself a priority without the rest of your life falling to pieces. Maybe that’s a post in itself.) It’s amazing, however, what we can unhook ourselves from when we get this self-care thing right. Finally, getting honest about what we’re really stuffing or pushing down or distracting ourselves from when we eat is critical. Releasing ourselves from the expectation and sensation of craving, for many of us, requires understanding what we’d rather not experience in its place.

Thanks for reading, everyone. What’s been your experience with craving? Where does the science make personal sense to you, and what feedback would you add? Have a great end to the week.