Research indicates that exercise that feels more like play (ie. those that are less complex) might have lasting health implications.
“Complex is Better” Bias in Health Judgments:
Evidence from Nutrition and Exercise Intervention Evaluation
By
Jacque R. Nyenhuis,1 Louisa Raisbeck,1 and Edward T. Cokely1,2
Michigan Technological University1
Max Planck Institute for Human Development2
Author Note – Correspondence concerning this article should be addressed to Jacque Nyenhuis at jrnyenhu@mtu.edu
Abstract:
Nutrition and fitness interventions have remarkably high failure rates (98%) for weight-loss maintenance. Based on these statistics it is critical to understand how nutrition and fitness interventions can be improved, possibly through adherence. Research indicates that perceived rule complexity of a program is among the strongest factors negatively affecting adherence. In our study, it is hypothesized that many people mistakenly believe that “complex is better” for nutrition and fitness programs and they underestimate the importance of adherence. A national, random survey was conducted to better understand the role of rule complexity in judgments and beliefs about nutrition/fitness interventions and their perceived efficacy. Performance and calibration data are assessed via surprise memory tests. Individual difference in nutrition/fitness knowledge, general abilities, and demographics are also assessed. Participants did see a large difference in the difficulty and complexity of specific interventions and at the same time showed a “complexity bias” in their judgment that the complex nutrition intervention would give better weight loss results. (ca. 10% better; Cohen’s d = .3) The results did generalize for the fitness programs. People accurately judged one program as more complex and harder to remember. Accurate recall and recognition of exercise rules was dramatically reduced for the complex program and participants incorrectly judged the complex program to be more effective for weight loss (ca. 20% better; Cohen’s d = .7). This research documents a “complex is better” bias when evaluating common nutrition and fitness (and perhaps other) health interventions. In this study, there were large mnemonic benefits of simpler interventions and evidence that the public does tend to understand that simpler interventions are easier to follow and adhere to. However, the data suggests a widespread lack of public understanding of the importance of adherence for weight loss.
Introduction:
Nutrition is an influential and modifiable factor in preventable chronic disease development (Byrd-Bredbenner & Abbot, 2009). It has been widely recognized as a field of contradictions in that as we learn more about nutrition and fitness, the leading health indicators have not shown significant improvement in preventable diseases where poor nutrition is a risk factor (Mokdad et al., 2003).
This study of facilitating nutrition planning and communication comprises a perceptional assessment approach. It is a look at the predicted effect that people perceive more complex nutrition and fitness interventions as having more impact and discounting the importance of adherence.
Today, roughly 63% of Americans are considered overweight, resulting in over 100 billion dollars in obesity-related medical costs (Healthy People, 2010; Hedley et al., 2004). Although dramatic, such costs do not capture many other important obesity-related personal and social struggles (Cataldo, Nyenhuis, and Whitney, 1989). Unfortunately, it is exceedingly rare for those who lose weight to maintain their weight loss for an extended period (98% failure rate; Jeffery et al., 2000, but see also Mann et al., 2007). How can we improve nutrition and health intervention adherence? Here, we investigate the role of rule complexity, by manipulating numeracy, in judgments about and memory for nutrition and fitness intervention efficacy. For example, despite a market full of complex interventions, research indicates that perceived rule complexity of an intervention is among the strongest factors negatively affecting adherence (Mata, Scheibehenne, &Todd, 2008; Wansink, 2008).
Many of the popular diets on the market such as Atkins, Ornish, Weight Watchers and Zone involve counting calories, calculating grams of fat or carbohydrate and determining weights or portion sizes (Dansinger, Gleason, Griffith, Selker, & Schaefer, 2005). These mathematical calculations of calories and grams require dieters to use analytical decision-making processes for each of many food and exercise decisions. Research shows that these diets do lead to short-term weight loss of about 5 to 10 percent but the losses are not maintained (Mann et al. 2007). Garner and Wooley (1991) reported that the only debate in weight loss is not when it will be regained, but how long it will take. Maybe we could justify dieting if we could say that at least we are getting healthier and our good intentions are enough. However, studies show that there is not a significant improvement in health in dieters (Mann et al., 2007) and Schwarzer et al. (2008) found that intentions are not a good predictor of adherence in exercise programs. If costs of diet and exercise programs were simply the possibility of failure, that would be bad enough. But there are cognitive implications that should be considered (Shaw & Tiggerman 2004).
As common and benign as dieting may seem, research has shown that it may affect cognitive functioning. Kemps, Tiggemann, & Marshall (2005) tested the working memory differences of dieters and non-dieters. Participants looked at words and location of words on a screen to test their working memory. Participants who were dieting performed worse on the memory tests than non-dieters. This supported the authors’ hypothesis that dieters have impairment in working memory. They attributed this impairment in working memory to an increased cognitive load. The authors reported that their data supported the idea that preoccupying thoughts of food, diet and body shape reduced the working memory available for other tasks.
Vreugdenburg, Bryan, Kemps (2003) looked at how weight loss diets affected working memory in participants of a study on mid-life health. The study had dieters and non-dieters work on math problems at the same time as other cognitive tasks so they could test the central executive, phonological loop and visuo-spatial sketchpad as it related to working memory. Dieters did worse in a dual task situation than non-dieters. The authors reported that dieters’ verbal comments indicated more preoccupying thoughts of food that divided their attention than in non-dieters.
Green and Rogers (1998) hypothesized that the mediating variable in the cognitive deficient is that of preoccupying cognition concerning food and body shape. An eating behavior questionnaire provided information to divide the participants into three groups for this study. The groups were either low or medium restrained eaters, highly restrained eaters or current dieters. A mental rotation task assessed the change between groups concerning the visuo-spatial sketchpad working memory. To test the storage capacity of the phonological loop portion of working memory, participants were given a reading span test. The participants verbally recalled numbers while letters appeared on the screen. Researchers found that planning times for the current dieting group on the tower of London task took longer than for the non-dieting group. Other tasks that increase use of the central executive and phonological loop were higher, also. Higher levels of complexity in tasks showed an increase in cognitive impairment in dieters.
A study by Mata et al. (2010) pointed out that the impairment in cognitive areas might be depleting the resources needed to keep track of calories, or memory recall for specifics needed to follow complex diet rules. Mata et al. (2010) suggests that the rules may seem even more complicated if there is cognitive impairment.
Rule complexity of diets was compared using a complex Weight Watchers diet and a diet published in a popular women’s magazine that was assessed as simpler (Mata et al., 2010). The complexity of the rules of each diet was determined by looking at what specific items they had to keep track of each day and which represented arithmetic processing demands. Participants answered a questionnaire online every 4 weeks. Statements were rated indicating complexity of the program and how long they planned to stay on the program. The researchers gave feedback to the participants after the third measurement or after dropping out. It was found that when diets were perceived as too complex, dieters were less likely to remember the rules of the diet, had more problems applying them and ended up more likely to give up on the entire weight loss plan.
Mata, Todd,. & Lippke (2010) found that rule complexity had the greatest impact on adherence to a diet program and Teixeira et al., (2010) found that one critical aspect for weight loss was a change from a rigid cognitive restraint pattern to a more flexible pattern. Cognitive restraint in this study was determined by a 21-item scale that measures attempts to control food intake. This study suggests that a more flexible weight loss program is worth investigating further. Nutrition and fitness programs with lower rule complexity could help individuals find a more flexible pattern such as the type the authors of this study found most effective.
Weight loss strategies but not specific plans were found to be beneficial in a study (Boutelle, Libbey, Neumark-Sztainer, & Story, 2009) where 62 adolescents who lost weight were compared to 68 who did not. The authors found that adolescents who lost weight were less likely to be on a specific weight loss plan. Many of the changes made by the participants were very simple and the study supports other research that reports dieting is not the answer to obesity (Mann et al., 2007) and that simple health plans can be effective (Gollwitzer, 1999). As early as 1987, research in animals showed that structured exercise interventions and eating ad lib did not lead to weight loss (Gibbons, Singleton & Nyenhuis, 1987). Complex programs that require attenuation, taking away valuable resources that could be used for nutrition and behavior changes can be self defeating (Mata et al., 2010).
The importance of a simple system that leads to adherence to nutrition and fitness interventions seems intuitive but research using food labels found a paradox when asking consumers which type of nutrition food labeling they prefer. There is a large body of research on simple versus complex nutrition labeling and many of the simpler systems proposed use a stop light or symbol instead of any numerical information. Even though participants could identify one label as easier to understand, the second more complex label (with more complex numerical information) was the label consumers said they preferred (Levy, Fein & Schucker, 1992). Other researchers looking at this bias attribute it to the idea that while consumers often say they like the detailed, numerical information, they may not sufficiently take into account the amount of effort required to use the numerical information (Herpen & van Trijp, 2011).
Numeracy can be simplified to a large extent in a nutrition or exercise prescription as seen in the simpler interventions in Appendix I. Even though consumers may see these simpler interventions as easier to adhere to, they may be impacted by the numerical information that makes one intervention look more complex and therefore more effective.
Many diet and exercise programs go against the way we make choices. If every choice was analytical and modeled the multi-attribute utility theory, maybe more success would be found in complex diet and exercise plans. In the real world, however; people are more likely to use fast and frugal heuristics to make food choices (Scheibehenne, Miesler, & Todd, 2007).
Scheibehenne et al. (2007) found that people make food choices based on rules of thumb. He found that choosing the number one priority for food decisions was just as accurate at predicting food choices as using a weighted additive mechanism. The author gives the example of using the lexicographic decision rule (LEX) in making food choices. Usually lexicographic decision rules (LEX) is used when a quick decision is needed and a mistake would not be costly (Giegerenzer, Todd & ABC Research Group, 1999). Scheibehenne et al. (2007) reports that this type of decision model predicts about as well as more analytical models, especially in choosing lunch dishes.
It is thought that similar fast and frugal heuristics will increase adherence to healthful nutrition and fitness for a lifetime. The nutrition and fitness changes that a dieter makes needs to be simple enough for the changes to become intuitive over the long-term.
Problem Statement/Rationale
We suggest that people often express a ‘complex is better’ bias when evaluating the efficacy of nutrition and fitness interventions (e.g., complex interventions produce more weight loss). Findings from this study may make an important contribution to science and society because many of the popular diets on the market involve counting calories, calculating grams of fat or carbohydrate and determining weights or portion sizes (Dansinger et al., 2005). These mathematical calculations of calories and grams require dieters to use analytical decision-making processes for each of many food and exercise decisions. Research shows that these diets can lead to short-term weight loss of about 5 to 10 percent but the losses are not maintained (Mann et al., 2007). Garner & Wooley (1991) reported that the only debate in weight loss is not when it will be regained, but how long it will take. Maybe we could justify dieting if we could say that at least we are getting healthier and our good intentions are enough. However, studies show that there is not a significant improvement in health in dieters. Mann et al. (2007) and Schwarzer et al. (2008) found that intentions are not a good predictor of adherence in exercise programs.
Hypothesis
The hypothesis of this study is that there is a ‘complex-is-better’ bias (i.e. increased complexity of numerical information) when evaluating the efficacy of nutrition and fitness interventions. Simple plans may be discounted by participants in favor of more complicated programs. Potential dieters look at the nutrition and fitness interventions and the more complex programs with rigid rules catch consumer’s attention. Weight loss is such a frustrating, complicated problem that possibly they want the biggest and most amazing-looking program available. However, it is hypothesized that the simpler programs are easier to remember and easier to maintain/implement for busy people. Using rules of thumb are thought to be more powerful in promoting adherence for weight loss control than complex rule-based nutrition and exercise plans. We further hypothesize that people often neglect adherence when making decisions about efficacy of nutrition and fitness plans.
Research Design
A series of two within-subjects experiments were conducted to investigate these hypotheses. The experiments include data on how participants evaluated the efficacy and ease of adherence to nutrition and fitness interventions manipulated in the level of numeracy.
Method
Participants aged between 18 and 67 years were surveyed using Unipark online survey software with paid participants from Amazon’s Mechanical Turks. Demographics of participants were 131 male and 182 female with 13% reporting diagnosis of high blood sugar or diabetes. In the sample, 44% of participants had body mass index (BMI) greater than 25% and 56% had BMI less than 25% (7% no answer). The demographics of participants were roughly similar to the demographics found in other studies of dieters. The percentage of participants with a lower BMI is consistent with other research data that shows self-report is often lower than actual report of height, weight and BMI (Gorber, Tremblay, Moher, & Gorber, 2007).
In experiment 1a, participants (n=313) were given two nutrition interventions to compare. The two interventions were designed to be representative of common options made available by diabetes educators, dietitians or other health care professionals (i.e., a “macronutrient” diet or a “plate” diet, see appendix I). Each intervention was further equated on number of rules, number of words and calorie level. The two interventions differ in that the macronutrient diet had a more complex level of numeracy in the rule descriptions than the simpler intervention. The name of the intervention with the higher level of numeracy used a quantitative term, “macro” in its title. However, the simpler diet was designed to be at least as effective as the more complex diet, with some data suggesting that it was likely to be more effective (Camelon et al., 1998). Participants were then asked to rate each intervention on a number of dimensions including (1) ease of remembering, (2) ease of adhering when hungry or under stress/time pressure, and (3) overall intervention efficacy in terms of expected weight loss in one month.
In Experiment 1b, the same participants were given two fitness programs to compare. The programs were equated on number of rules, number of words and exercise prescription level (and thus are similar in terms of efficacy; Skinner, 2005). The major differences between the two programs was the complexity which was manipulated by including a higher level of numeracy for the rules of one of the programs. Participants were then asked to rate each program on a number of dimensions including (1) ease of remembering, (2) ease of adhering when under stress/time pressure, and (3) overall program efficacy in terms of expected weight loss in one month. Lastly, participants were given a surprise memory test for both the diet and exercise interventions. The study examined the subjective complexity of the interventions by rating how they perceived specific cognitive tasks that might be required if they were going to be on one of the programs. Performance and calibration data are assessed via surprise memory tests. Individual difference in nutrition/fitness knowledge, general abilities, and demographics were assessed using SPSS statistical software.
Results
We found that participants did see a large difference in the difficulty and complexity of specific interventions and at the same time showed a “complexity bias” in their judgment that the complex nutrition intervention would give better weight loss results (ca. 10% better; Cohen’s d = .3). The results did generalize for the fitness programs. People accurately judged one program as more complex and harder to remember. Accurate recall and recognition of fitness rules was dramatically reduced for the complex program and participants incorrectly judged the complex program to be more effective for weight loss (ca. 20% better; Cohen’s d = .7). This research documents a “complex is better” bias when evaluating common nutrition and fitness (and perhaps other) health interventions. In this study, there were large mnemonic benefits of simpler interventions and evidence that the public does tend to understand that simpler programs are easier to follow and adhere to. However, the data suggests a widespread lack of public understanding of the importance of adherence for weight-loss success
Experiment 1a and 1b showed a modest to medium-sized effect for “complex is better” for weight loss. Participants estimated the more complex intervention to be 10 to 20% better even though the simpler nutrition and fitness programs have been seen in some research to perform better and was perceived by the participants themselves as simpler, easier to adhere to and easier to remember. A surprise memory test showed that participants were in fact able to remember the rules for the simpler interventions better.
Our results suggest that even though previous research has shown that less complex interventions increase adherence and therefore efficacy (Nauret, 2010), there may be a “complexity bias” in that people judge the very interventions that might be difficult to adhere to as more effective. If individuals believe regimens that they perceive as more complex as better, it may be because they cannot conceive of a simple solution to such a complex problem. This is in contrast to the research that shows that adherence is better when there is lower perceived rule complexity (Mata et al 2010). There may be a connection between rule complexity and the high rate of failure of nutrition and fitness programs.
Implications and Conclusions
The implications for rule simplicity are boundless. It is thought that rule simplicity provides the advantage of decreased cognitive load and increased adherence. This paper is not designed to espouse that complex diet and exercise interventions be forgotten. It is to present the idea that there are other ways to make decisions about nutrition and fitness and these processes need to be explored, cultivated and incorporated into the intuitive nature of the person who wants healthful nutrition and fitness for a lifetime. Today’s food and fitness environment is unique. Uncertain, dynamic, high-level stress and minimal time are constraints that make it so hard for us to conduct an analytical decision-making process to determine the best course of action. Even if simple rules that become intuitive turn out to be difficult to adhere to, the cost is very low. Complex diets that fail have much higher costs in terms of money, time and divided attention. In the final analogy, every nutrition and fitness decision is determined by a situation. Each situation is different and requires a simple heuristic that will not just fit, but will predict.
A limitation of this study is the impact of the placebo effect. The ‘complex is better’ bias does give room for the possibility that some interventions work because the participants believe they are better. It is also possible that some people do not mind investing all their energy, cognitive processes and time into a complex program. These individuals may not value efficacy of interventions as much as the process and commitment to an arduous, difficult goal regardless of the outcome. A second limitation is that while participants clearly indicated that they believed the complex interventions would lead to more weight loss, another question about which program they would choose showed variability. This suggests that perceptions of interventions with more complexity (i.e. higher levels of numeracy) might have a bias attribute difference similar to research results compiled by Herpen and van Trijp (2011). They concluded that while consumers often highly appraise detailed, numerical information they may not feel competent in personal use of complex numeracy. Additional research into these attitudes is warranted.
The current research is among the first to examine how rule complexity affects judgments of nutrition and fitness interventions—i.e., socially and economically important issues. Theoretically, results contribute to our understanding of biases that partially moderate nutrition and fitness intervention selection and may mediate adherence. Results may also contribute to a better understanding of the dynamic ecology of judgments about nutrition and fitness interventions, using representative stimuli (i.e., professionally developed interventions), highlighting the interplay among persons (abilities), processes (heuristics), and environments (cue‐complexity) (Cokely, 2009).
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Appendix I Actual questions and description of stimuli:
Diet in America
- Most Americans are overweight. Medical science shows that the risks are high for the 190 million who are overweight.
- At some point in their lives, many Americans are told they need to lose weight…
Decision Task
Imagine you wanted to go on a diet to lose a significant amount of weight. Two diets are available. Assume that all the support and information for each diet is available to you. Read through the following two diets carefully. Answer the questions that follow.
| PLATE DIET | MACRONUTRIENT DIET |
| Rule #1 3 meals per day that fit on an 8 inch plate | Rule #1 1800 calories per day |
| Rule #2 5 fruits or vegetables per day | Rule #2 15% calories from protein (56 grams protein) |
| Rule #3 Unlimited non–caloric drinks (water, tea, etc.) | Rule #3 25% calories from fat (41 grams fat) |
| Rule #4 Write down everything you eat in a food journal. | Rule #4 60% of calories from carbohydrate (225 grams carbohydrate) |
CHECK HERE o CHECK HERE o
I have read this Program I have read this Program
How hard will it be to remember the rules for each diet?
Not hard Very hard
Plate Diet 1 2 3 4 5 6 7
Macronutrient Diet 1 2 3 4 5 6 7
How much weight do you think you could lose on each diet in one year?
Plate Diet 0 to 5 lbs 6 to 10 lbs 11 to 15 lbs 16 to 20 lbs 21 lbs or more
Macronutrient Diet 0 to 5 lbs 6 to 10 lbs 11 to 15 lbs 16 to 20 lbs 21 lbs or more
How hard is each diet to follow?
Not hard Very hard
Plate Diet 1 2 3 4 5 6 7
Macronutrient Diet 1 2 3 4 5 6 7
How effective would each diet be?
Not Effective Very Effective
Plate Diet 1 2 3 4 5 6 7
Macronutrient Diet 1 2 3 4 5 6 7
How complex is each diet?
Not Complex Very Complex
Plate Diet 1 2 3 4 5 6 7
Macronutrient Diet 1 2 3 4 5 6 7
If you were really hungry, how hard would it be for you to stick to each diet?
Not hard Very hard
Plate Diet 1 2 3 4 5 6 7
Macronutrient Diet 1 2 3 4 5 6 7
How difficult would following each diet be compared to preparing a four-course meal?
Less Difficult More Difficult
Plate Diet 1 2 3 4 5 6 7
Macronutrient Diet 1 2 3 4 5 6 7
How hard would it be to make a meal in five minutes following each diet?
Not hard Very hard
Plate Diet 1 2 3 4 5 6 7
Macronutrient Diet 1 2 3 4 5 6 7
How confident are you that you could maintain each diet and follow the diet’s rules?
Not Confident Very Confident
Plate Diet 1 2 3 4 5 6 7
Macronutrient Diet 1 2 3 4 5 6 7
How many diets have you tried in an attempt to deliberately lose weight?
No diets
1 to 3 diets
4 to 6 diets
More than 6 diets
Have you ever known anyone on a diet like either of these diets?
Plate Diet No Yes
Macronutrient Diet No Yes
If you wanted to lose weight fast, which diet would you choose?
Macronutrient Diet o Plate Diet o
Decision Task
Imagine you wanted to start an exercise program to lose a significant amount of weight. Two programs are available. Assume that all the support and information for each program is available to you. Read the following two programs carefully. Answer the questions that follow.
| CARDIOVASCULAR PROGRAM | WALKING PROGRAM |
| Rule #1 30 minutes aerobic exercise/day. | Rule #1 Walk for 30 minutes each day. |
| Rule #2 Exercise at 60% to 70% of VO2 max. | Rule #2 Walk at a speed so that breathing is heavy but you are still able to talk. |
| Rule #3 Train on ab machine at 80% max (2 sets of 25 each) | Rule #3 50 sit-ups |
| Rule #4 Train on bench press at 50% max (1 set of 15) | Rule #4 15 push ups |
CHECK HERE o CHECK HERE o
I have read this Program I have read this Program
How hard will it be to remember the rules for each program?
Not Hard Very Hard
Cardiovascular program 1 2 3 4 5 6 7
Walking program 1 2 3 4 5 6 7
How much weight do you think a person could lose on each program in one month?
Cardiovascular program 1 lb 2 lbs 3 lbs 4 lbs 5 lbs 6 lbs 7 lbs 8 lbs 9 lbs 10 lbs
Walking program 1 lb 2 lbs 3 lbs 4 lbs 5 lbs 6 lbs 7 lbs 8 lbs 9 lbs 10 lbs
How hard is each program to follow?
Not Hard Very Hard
Cardiovascular program 1 2 3 4 5 6 7
Walking program 1 2 3 4 5 6 7
How effective would each program be?
Not effective Very effective
Cardiovascular program 1 2 3 4 5 6 7
Walking program 1 2 3 4 5 6 7
How complex is each program?
Not Complex Very Complex
Cardiovascular program 1 2 3 4 5 6 7
Walking program 1 2 3 4 5 6 7
If you were really tired/busy, how hard would it be for you to stick to each program?
Not Hard Very Hard
Cardiovascular program 1 2 3 4 5 6 7
Walking program 1 2 3 4 5 6 7
How would following each program be compared to working with a trainer?
Easier Harder
Cardiovascular program 1 2 3 4 5 6 7
Walking program 1 2 3 4 5 6 7
How long would it take you to finish your workout?
Cardiovascular program 30min. 45min. 60min. 75min. 90min. 105min. 120min.
Walking program 30min. 45min. 60min. 75min. 90min. 105min. 120min.
How likely is this program to improve your fitness and health?
Not Likely Very Likely
Cardiovascular program 1 2 3 4 5 6 7
Walking program 1 2 3 4 5 6 7
How many exercise programs have you tried in an attempt to deliberately lose weight?
o None
o 1 to 3
o 4 to 6
o More than 6
Have you ever know anyone using these exercise programs?
Cardiovascular program o No o Yes
Walking program o No o Yes
If you wanted to lose weight fast, which diet would you choose?
Cardiovascular Program o Walking Program o
Appendix II.
Actual Nutrition and Fitness Stimuli with Data.
