January 12, 2018

People tend to eat more food when a larger variety of food is available (McCroy, Fuss, & McCallum, 1999; Rolls, Rolls, Rowe, & Sweeney 1981a; Smiciklas-Wright, Kreb-Smith, & Krebs-Smith, 1986).  This variety effect of food has been found to enhance consumption in a  different areas, in bother genders and across a wide range of ages (for reviews see Wansink, 2004; Raynor & Epstein, 2001).  The tendency to ingest a variety of foods may be an evolutionary development that helps ensure that a sufficient quantity of essential nutritients is consumed (Raynor & Epstein, 2001) while reducing the chances of any given food’s toxicity having a negative impact on health (Rozin & Rozin, 1981). “The variety effect is particularly interesting, as its influence might be partly due to variety, just for the sake of variety” (Hale & Varakin, 2016, p.204)

While between meal variety influences consumption over the course of several days (Stubbs, Johnstone, Mazian, Mbaiwa, & Ferris, 2001), most research (including the current experiment) focuses on the effect of within meal variety (Raynor & Epstein, 2001; Remick, Polivy, & Pliner, 2009).   For example, in one study, participants who were offered a total of 3 different flavors of yogurt consumed more than participants who were offered a single color (Rolls, Rowe, Rolls, Kingston, Megson., & Gunary, 1981b).  In another, participants who were offered a variety of different types of sandwiches consumed more than those who were offered less variety (Rolls, et al., 1981b).

Given that food is an inherently multi-modal stimulus – activates various sensory pathways (Verhagen, 2007), it is perhaps not surprising that increased variety on non-flavor related dimensions of food can also lead to increases in consumption ( Rolls, Rowe, & Rolls, 1982).  In one study, changes in the shape of three successive courses of pasta led to a 14% increase of food intake compared to a condition where the shape was held constant for each course (Rolls et al., 1982).

Being unaware of external factors’ influence on food consumption has important implications in regards to controlling eating behavior.  If unaware of how external factors influence consumption, it will be difficult to control eating behavior.  In a recent study, Dr. Varakin and I  directly tested whether people are generally unaware of external factors’ influence on food consumption, using the variety effect as a test case (Hale & Varakin, 2016). In our study we investigated whether or not participants would eat more M&M’s from a bowl containing a single color versus a bowl containing a variety of colors.  We were also interested in whether or not people who eat more M&M’s from the multi-color bowl would be aware they did so, and in addition, if they would indicate they ate more due to variety. Awareness, as discussed in our study, refers to a subjective state of being cognizant or conscious of something (Reber, 1985).  People often fail to accurately report factors that influence their thinking or behaviors (Nisbett & Wilson, 1977).  This was shown by a review of the existing literature and set of Nisbett & Wilson’s own experiments. Nisbett and Wilson inferred that individuals are sometimes unaware of the existence of a stimulus that influences their behavior, are unaware of the response, and are unaware that the stimulus has affected the response.  Other research has shown that perception (organization of sensations into meaningful patterns, interpretation of stimuli) can occur in the absence of awareness (Merikle et al., 2001). The info.. you are aware of is the information that shows up in working memory. The results of our study showed participants ate more M&M’s from the multi-color bowl than the single-color bowl.  Importantly, participants who ate more from the multi-color bowl were more likely to mention variety as a reason for the increased consumption than those who did not eat more from the multi-color bowl.  These results suggest that people are often aware of the variety effect, and are therefore inconsistent with the idea that people are generally unaware of how at least one external factor influences food consumption.  In the Discussion section we address limitations, possible criticisms, the need for future research and implications regarding external validity and statistical procedures. Awareness is on a continuum and temporal factors must be considered.  Suggesting that individuals might  be aware (conscious of) the variety effect in regards to food shouldn’t  be taken to mean that other  factors that influence eating are available to awareness.

Generally, if more food choices are available more food will be eaten. This isn’t always a bad thing. As an example, when attempting to increase the consumption of nutritious foods increase the number of nutritious food options.  In addition to the variety effect, there are other factors  that influence eating. Those factors are not within the scope of this article. For a detailed discussion on other factors involved with eating refer to – Why Are You Eating That

In a recent conversation with  Mariana Molinari Abadie she provided me with some eating suggestions she sometimes gives her clients. She was quick to point out, she doesn’t like to over generalize her recommendations on eating. Her recommendations are mostly based on individual needs. Follow Mariana on Facebook

Commentary from Mariana Molinari Abadie

I usually don’t give generalized tips; I like to provide solutions to personal limiting factors. Many folks are unaware of the many physiological and psychological factors that relate to eating. When attempting to assist clients in goal attainment I address physiological and psychological effects of long term dieting and restrictions, and I address other things they may feel are limiting factors. Unless I see a need to refer them to a registered dietitian, I try to work with what they are willing to share and help them overcome their personal obstacles. I try to work around their habitual diet for sustainability; instead of asking them to change, eliminate or restrict, I ask them to add something that can be beneficial. Something that is pleasant, and would be easy to accomplish. It is important to focus on one single addition or behavior at a time, until it becomes habitual. In other words, finding a way to reduce caloric intake that is not restricting, nor unpleasant and can be easily maintained once it becomes a habit. Sometimes it is not about, only their diets, but about moving more, and a simple addition like a 10 minute daily walk after lunch may be beneficial.

Changes can be as easy as- adding one fruit to your daily lunch, vegetables to every meal, a portion of protein with every meal, eating mindfully and stopping when you are 80% full, placing fruits and vegetables in a visible areas, storing the more tempting less nutritious foods away from view, making a grocery list, limiting “dessert” type foods to one at a time. The more choices we have the more we’ll want to try. But no matter the behavior, technique, or plan that works best for you, avoid dichotomous thinking and allow imperfections. The imperfect plan you can follow works much better than the perfect one you don’t. [Words of Wisdom]. Strict diets lead to the never ending restrict/binge cycles and may involve excessive stress. Relax and be kind to yourself; it’s OK to have your favorite foods in moderation, which brings me to the concept of compulsive snackers.

For compulsive snackers I found that what works well is to ask them to stick to 3 or 4 full meals, and snack only on fruits or vegetables. They can still have their sweets, nuts, or desserts if they feel like it, but as part of their meals and not in between them, leaving the most palatable foods for the end of the meal. Satiety plays an important role here, so they tend to consume less of the calorie dense food reducing the overall caloric intake of the meal. Some people need more structure, and they tend to adapt well to a few simple changes. Then again, it depends on the individual and their particular needs.

Lastly, remember that our bodies do not work on a daily schedule but on a time period, whether that is a day, a week, or a month. One day of a higher caloric intake is, not a failure; it can be perfectly included and even planned in a weekly/monthly deficit. Any strict regimen consisting of low calories or low carbohydrates can be very taxing, especially over a long-term period. If you cycle days of lower and days of higher calories, you can give yourself day breaks when you need it most; those days can be planned or forgiven if you happen to increase calories by accident one day. It’s O.K. to allow enough wiggle room when needed to help with adherence and sanity.

Large portions of this paper are derived from- Awareness of the Influence a Variety of Food has on Food Consumption (Hale & Varakin, 2016).


Results-Concise (Hale & Varakin, 2016)

“The effect of variety was statistically significant, F (1, 42) = 5.27, p < .05, partial ƞ2 = .11. The effect for bowl position was not statistically significant, F (1, 42) = .002, p > .05, partial ƞ2 < .001. The interaction, variety by bowl position, was not statistically significant, F (1, 42) = .059, p > .05, partial ƞ2 < .001. Participants ate an average of 12.5 M&M’s (SD= 17) from the multicolor bowl and an average of 8.5 (SD= 12.0) from the single color bowl. Thus, the variety influenced consumption.” The difference between the amount of M&M’s consumed, when comparing group data for single color bowl vs. multicolor bowl was large enough to suggest that the finding wasn’t due to unsystematic processes (chance).  Whether the bowl of multicolor M&M’s appeared to the left or right of the participant had minimal impact on eating. There was no interaction effect (non-multiplicative) in regards to variety (single or multicolor) with bowl position (left or right). When there is an interaction effect the effect of one independent variable (predictor) depends on the level of the other independent variable.  Important point: the numbers for stats are averages (aggregate); they are not individual numbers.  Individual scores are generally not provided in Results section. Some of the participants in this study ate more from the single color bowl and some ate an even amount from both bowls.

” A pair of 2 x 2 chi-square tests with A pair of 2 x 2 chi-square tests with actual consumption (showed variety effect vs. not) and cited reason for consumption (variety mentioned vs. not) as factors was used to test if the proportion of participants mentioning variety as a reason for consumption differed between participants who showed the variety effect, and those who did not. Regardless of which coder’s data was used, the difference was statistically significant, main coder: χ2 (N = 44, 2) =6.38, p < .02.; blind coder: χ2 (N = 44, 2) = 5.69, p < .02. Thus, these actual consumption (showed variety effect vs. not) and cited reason for consumption (variety mentioned vs. not) as factors was used to test if the proportion of participants mentioning variety as a reason for consumption differed between participants who showed the variety effect, and those who did not. Regardless of which coder’s data was used, the difference was statistically significant, main coder: χ2 (N = 44, 2) =6.38, p < .02.; blind coder: χ2 (N = 44, 2) = 5.69, p < .02. Thus, these results support the hypothesis that there is a relationship between actual and reported consumption: participants who actually consumed more M&Ms from the multi-color bowl were more likely to mention variety as a reason for consumption than participants who did not consume more M&Ms from the multi-color bowl.” Chi-Square tests, involve examining how well an observed distribution of scores corresponds with the expected distribution. A significant difference between observed distribution of scores and expected distribution indicates the differences  were probably systematic. Keep in mind, there is always chance of Type 1 error (false positive), so it is to be appreciated that outcomes are uncertain and logic follows from predictive science that outcomes be placed on a predictive continuum.

from Discussion

“Despite these limitations, the current results are important in demonstrating that some people are not completely unaware of at least one external factor’s relationship with food consumption. Of course, we are not suggesting that people are always aware of why they are eating what they are eating. However, the current results do not support the strong claim that people are almost always unaware of how external factors influence food consumption.”

Hale, J., & Varakin, D.A. (2016).  Awareness of the influence a variety of food has on food consumption. North American Journal of Psychology, 18(2), 203-210.

References are available upon request