Imagine the following scenario:
You go out to eat at a very nice restaurant. You share a few appetizers with your friends, have a beer, and enjoy a delicious steak and baked potato. After dinner, your friends talk you into splitting a piece of chocolate cake. Even though you’re pretty full, you can’t resist the cake so you have several bites. You enjoyed the meal but go home regretting you ate so much. The next morning you weigh yourself to see how much damage was done. To your delight, you don’t really notice any significant changes to your weight, so you go on with your day as usual. Maybe you eat a little less than usual to make up for the extra calories from the night before. But chances are, you don’t fully compensate for your splurge. Over time, these small doses of overeating add up, making it hard to maintain weight.
In the age of growing rates of obesity, our difficulty in maintaining normal weight is also a growing concern. On average, Americans gain about a pound each year. A pound doesn’t sound so bad, and year after year people probably barely even notice. But over 10 years this can matter quite a lot. Not only is it hard to lose weight, it’s also hard to just maintain weight.
Understanding the precise relationship between what we consume and the impact on our weight is actually quite difficult. It’s like trying to determine the impact of one home’s energy use on the rate of global warming. We know there is a relationship, but it’s hard to know exactly what that relationship is. First of all, there’s a lot of natural variation in our weight and in our diets. A few pounds of fluctuation each day can be totally normal, and most people don’t eat the same thing every single day. Also, our weight can go up or down by two pounds just depending on how much water we’ve had recently. Then, consider that excess food doesn’t convert to fat immediately.
New research from the Duke researchers at the Envolve Center for Health Behavior Change™, published this month in the journal Appetite, explains how our lay beliefs, or naïve models, lead us to faulty assumptions about how our “dietary splurges” impact our weight, resulting in a lack of compensation following these indulgences and self-serving biases.
Across six studies, the researchers showed that people have distorted ideas for how weight change works — specifically after single instances of overeating. In general, people convince themselves that weight loss will happen much faster than it actually will and that small amounts of weight gain are only temporary, disappearing without any dieting attempts. Even more interesting is that people seem to do this in a self-serving way — we can much more accurately predict the rate of weight loss in others than in ourselves. Sadly, since people believe weight loss happens more quickly and easily after overeating, the paper found that people also fail to compensate enough after overeating. This means that people don’t diet enough when they overeat because they trick themselves into believing the effects are short-lived and less consequential than they actually are.
In real life, this is probably a vicious cycle where we have a hard time noticing small changes when there are lots of things that impact our weight. At the same time, we enjoy, and should be able to enjoy, nice meals from time to time, without worrying about long-term health consequences. We just need better strategies for dealing with these indulgences so we can have our cake and eat it too (pun intended).
So, what should we do about this? One interesting finding from the paper was that participants reported that they would try to reduce their calorie consumption after overeating, but they matched the timeline of their reductions to the timeline of their consumption. If they overate for a week, they compensated for a week, but if they overate on one day, they compensated for only a few days – even if calorie amounts were the same in both cases. So, perhaps we can give people easier rules of thumb for compensating after overeating. For example, if you indulge at a restaurant, that may require four days instead of two days of cutting back. Or, we could help people cut back in larger quantities more quickly, through methods like intermittent fasting. But people should get medical approval first and supervision while fasting. Ultimately, education or calorie-counting strategies probably aren’t enough to help overcome this bias that is more about self-protection than information. And for those with patterns of overeating, more guidance from professionals such as social workers, registered dieticians and psychologists may be indicated.
About the Authors
Rachel Kahn is a behavioral researcher on the Better Living and Health Group at the Center for Advanced Hindsight at Duke University. She has a BS in biomedical engineering and a strong background in social psychology. She works with the Envolve Center’s Behavioral Economics (BE) team, which incorporates BE and social science into health-related behavioral modification programs.
Julia O’Brien is a principal behavioral scientist and leads the Better Living and Health Group at the Center for Advanced Hindsight at Duke University. She has a Ph.D. in social psychology and a background in product research. She also works with the Envolve Center.
About the Envolve Center for Health Behavior Change™
The Envolve Center for Health Behavior Change™ is a community-corporate-academic healthcare partnership that advances life-centric health research to improve lives so that communities can thrive. For more information regarding the Envolve Center for Health Behavior Change, visit https://envolve.wustl.edu.