Stress tends to mess with our eating habits. In times of stress, some people eat more, while others eat less. The type of food people eat also changes: compared to non-stressed individuals, stressed individuals more often eat unhealthy foods.

Laboratory experiments have shown that stress causes people to make unhealthier food choices. In a typical experiment, participants are exposed to an acute stressor, for instance, they are asked to present themselves before strangers, or to solve a very difficult puzzle within an unrealistically short timeframe. Unknown to the participants, the most important part of the experiment takes place during the breaks, when they are offered food and drinks. Secretly, the researchers observe exactly what the participants eat and drink. They look for differences between those who were exposed to stress prior to the break, and those who were not. And indeed, researchers do typically find differences between these groups. For instance, women who were most sensitive to stress (as shown by an exaggerated cortisol response), also ate more calories in response to stress [1]. In a second experiment, participants who had just performed several difficult tasks in front of a judge, especially those who reported being subjected to chronic stress in daily life, ate more chocolate cake and fewer vegetables compared to non-stressed participants [2].

But how do such laboratory experiments relate to real-life? After all, for most of us, giving presentations is not the most influential stressor in our lives, and real-life situations are much more complex. To investigate how real-life stressors affect food choices, one needs so-called epidemiological studies. In such studies, large groups of people are followed over longer periods of time. At multiple time points, they are asked about their stress levels (including daily hassles, work-related stress, academic stress, etc.) as well as about their eating habits. Consistent with experimental studies, epidemiological studies have shown that, on average, diet quality is lower in people who report more stress (e.g. [3] [4]). However, the effects reported in real-life studies are much smaller compared to the effects reported in the lab: in real life, stress is only one among many factors influencing your food choices.

So exactly how big ís the effect of real-life stress on our real-life food choices? We investigated this in over a hundred thousand people from the North of the Netherlands. We found that exposure to stressful life events, such as the loss of a family member or being the victim of a crime, was associated with poorer diet quality; however, the effects of stress were relatively small. For instance: on average, most people reported having dealt with one stressful life event in the past year, and their average diet quality score (on a scale of 0-48) was 23.9 points. People who reported dealing with two instead of one stressful events had an average diet quality of 23.8 points. For comparison, the difference in diet quality between the average man (22.5 points) and the average woman (24.9 points) in our study was 27 times bigger [5].

To summarize, diet quality deteriorates in times of stress. However, in real life situations, with a multitude of other factors determining what, where and when we eat, the effect of stress alone is very small.

Do you want to learn more about brain changes underlying the effect of stress on food choices? Check out this blog: https://newbrainnutrition.com/stress-and-nutrition-hungry-brain/ by Simone Demmel.

REFERENCES:
[1] Epel, E, Lapidus, R & McEwen, B, Brownell, K (2001). Stress may add bite to appetite in women: a laboratory study of stress-induced cortisol and eating behavior. Psychoneuroendocrinology, 26(1), 37-49

[2] Tryon, MS, DeCant, R, Laugero, KD (2013). Having your cake and eating it too: a habit of comfort food may link chronic social stress exposure and acute stress-induced cortisol hyperresponsiveness. Physiology and behavior, 114-115, 32-37

[3] Mikolajcyk, RT, Al Ansari, W & Maxwell, AE (2009). Food consumption frequency and perceived stress and depressive symptoms among students in three European countries. Nutrition Journal, 8(1),1-8

[4] O’Connor, D, Jones, F, Conner, M, McMillan, B, Ferguson, E (2008). Effects of daily hassles and eating style on eating behavior. Health Psychology, 27(1 supplement).

[5] Schweren et al., in preparation

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Have you ever done your weekly grocery shopping and ended up with more than actually written on your grocery list?
Everybody has at least once experienced how it is to buy food in a supermarket with hunger and buy much more than planned. The widely known recommendation: Never go grocery shopping when you are hungry!!!

But is it only a myth or is there a grain of truth in that advice?
What exactly is the issue with going grocery shopping when you are hungry? If you do you probably buy more food than you need and planned to buy. Additionally, unhealthy food might be much more attractive for you than healthy food. The consequence: you have more food at home, so you might eat more and unhealthier. Imagine you are hungry and are coming home from work after a stressful day and now you get to choose between a frozen pizza and a healthy meal that has not been prepared yet – What would you choose? In that situation, I think I would definitely choose the frozen pizza.

High-calorie food and unhealthy food are associated with obesity. Obesity research found a moderate relationship between obesity and emotional disorders like depressive disorder and anxiety disorder (1). Thus, having fast food frequently might not only affect your physical, but also your mental well-being.

Let’s rewind to grocery shopping, but now consider you are not hungry. You probably would only buy the things that are on your grocery list, and also rather healthy food than an unhealthy one. So now you come home hungry from a stressful day at work and you don’t have the choice between healthy and unhealthy food, and the temptation of the frozen pizza isn’t there. So you would start to prepare your healthy food and thus automatically eat healthier.

Coming back to the question if these scenarios are devised or true, and thus representative for weekly grocery shopping.
Research has shown that impulsivity, obesity, and food buying behavior are related. People with obesity are more impulsive than slim people. Also, impulsive people eat more than less impulsive people. Hunger influences food buying behavior and food consumption, especially of high caloric food. The relationship between impulsivity and buying food might be state dependent: researchers have found that impulsive people bought more calories, especially from snack food, but only when they were feeling hungry. This means that impulsivity and hunger interact in their influence on consumption. Obese people are found to show a preference for energy-dense, high-fat food and eat more of these foods, compared to slim people (2).

So what’s the conclusion?
Yes, hunger influences your grocery shopping, especially in interaction with impulsivity. If you consider yourself an impulsive person, you might be more prone to buying more than intended when you go shopping hungry.

So if you have the chance: only go shopping for groceries when you are full and focused. If you accidentally get into a hungry grocery shopping situation, keep this blog in mind and try to focus on your grocery list.

REFERENCES:
Scott, K. M., Bruffaerts, R., Simon, G. E., Alonso, J., Angermeyer, M., de Girolamo, G., … & Kessler, R. C. (2008). Obesity and mental disorders in the general population: results from the world mental health surveys. International journal of obesity32(1), 192.

Nederkoorn, C., Guerrieri, R., Havermans, R. C., Roefs, A., & Jansen, A. (2009). The interactive effect of hunger and impulsivity on food intake and purchase in a virtual supermarket. International journal of obesity33(8), 905.

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We, human beings in Western society, make over 200 food choices each day (1). That’s a lot! Fortunately (or, according to others, unfortunately), we don’t actually have to think about each and every one of them, or at least not consciously. If our food choices are not so much a conscious decision, then how do we make them? A lot has been written about external factors influencing our food choices, for instance, alluring displays in supermarkets or the availability of unhealthy foods in our day-by-day environment. In this blog, I will address the potential role of genetics on food choices: to what extent do our genes determine what we eat?

Eating behaviours are complex, i.e. they are very diverse and influenced by many different factors. When we investigate complex behaviours, we are unlikely to find simple explanations. In other words: we do not expect to find one gene that makes me prefer pizza margarita over pizza fungi, nor will we find a single gene responsible for my triple-chocolate ice cream consumption. There are, however, some instances in which specific genes have relatively simple and straightforward effects on our food choices. This is the case when genetic variants code for food sensitivities.

A famous example is the LCT gene (or, more precisely, the C>T change at 13910 bases upstream of the LCT gene in the 13th intron of the MCM6 gene). The LCT gene codes for lactase persistence, or lactose tolerance after childhood. Worldwide, the majority of people (and most other mammals, for that matter) no longer tolerate dairy products after childhood. For them, consuming milk products causes nausea, bloating and cramping within 2-3 hours. As a result, they will soon learn not to consume dairy products. Those who have the lactase persistence gene, however, don’t have any problems digesting dairy products and, thus, are more likely to consume them (2). Geographical region is important here: while in Northern European countries such as the UK and Finland, 90-100% of people tolerate dairy products, in South-East Asia and Australia this number is close to 0% (3).

A similar situation seems to occur for genes coding for certain taste receptors on the tongue. The TAS2R38 gene, for instance, makes some people extremely sensitive to bitter taste. This, of course, will cause them to avoid bitter foods such as cruciferous vegetables (4). A recent study has even identified a small number of genes that together cause people to either love or hate marmite (5)! Another gene variant (CYP1A1), coding for caffeine clearance from the body, causes carriers to drink less or more coffee and tea (6).

Thus, when food sensitivities are involved, food choices can be driven by specific genes. Most food choices, however, have very little to do with food sensitivities and are much more complex. Pizza Margarita or Pizza Funghi? Triple-chocolate ice cream today or maybe tomorrow? While for such complex food choices there is no single gene responsible, our genetic make-up still does have influence. Typically, for complex behaviours, many different genes can be identified. While each gene individually contributes only a little bit, together they can actually have quite an effect on your food choices. For instance, a recent study identified seven genetic variants each having a small effect on carbohydrate intake. Taken together, genes explained 8% of the variation in carbohydrate intake between individuals (7).

In conclusion: while some genetic variants have rather drastic effects on our food choices, by giving us a physical adverse reaction to certain foods, there are only few of them. Most of our food choices are much more complex. These are influenced by multiple genes at the same time, and even together these genes have only limited influence.

REFERENCES
1. Wansink, B., & Sobal, J. (2007). Mindless eating: The 200 daily food decisions we overlook. Environment and Behavior, 39(1), 106-123. doi: 10.1177/0013916506295573

2. Szilagyi, A. (2015). Adaptation to Lactose in Lactase Non Persistent People: Effects on Intolerance and the Relationship between Dairy Food Consumption and Evolution of Diseases. Nutrients, 7(8):6751-79. doi: 10.3390/nu7085309

3. Itan, Y., Jones, B.L., Ingram, C.J.E., Swallow, D.M. & Thomas, M.G. (2010). A worldwide correlation of lactase persistence phenotype and genotypes. BMC Evol Biol, 10:36. doi: 10.1186/1471-2148-10-36

4. Feeney, E., O’Brien, S., Scannell, A., Markey, A. & Gibney, E.R. (2011). Genetic variation in taste perception: does it have a role in healthy eating? Proc Nutr Soc, 70(1):135-43. doi: 10.1017/S0029665110003976.

5. Roos, T.R., Kulemin, N.A., Ahmetov, I.I., Lasarow, A. & Grimaldi, K. (2017). Genome-Wide Association Studies Identify 15 Genetic Markers Associated with Marmite Taste Preference. BioRxiv (preprint). doi: 10.1101/185629

6. Josse, A.R., Da Costa, L.A., Campos, H. & El-Sohemy, A. (2012). Associations between polymorphisms in the AHR and CYP1A1-CYP1A2 gene regions and habitual caffeine consumption. Am J Clin Nutr, 96(3):665-71. doi: 10.3945/ajcn.112.038794.

7. Meddens, S.F.W., de Vlaming, R., Bowers, P., Burik, C.A.P., Karlsson Linnér, R., Lee, C., et al. (2018). Genomic analysis of diet composition finds novel loci and associations with health and lifestyle. BioRxiv (preprint). doi: 10.1101/383406

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