Willpower (or Lack of It) Is the Wrong Way to Think About Weight

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When you succeed at eating healthy foods and avoiding junk, you probably attribute the bulk of your success to your ability to resist unhealthy impulses, the sheer power of your mighty will. Likewise, when the diet (inevitably) fails and you start to regain the weight you lost, it’s your inability to exert self-control that takes much of the blame. 

It’s true that self-control is a powerful human tool, and that people with a lot of it are more likely to do better in school and work than those with comparatively little of it. But when it comes to weight loss (and gain), willpower is not actually all that powerful, argues University of Minnesota health psychologist Traci Mann in her new book, Secrets From the Eating Lab: The Science of Weight Loss, the Myth of Willpower, and Why You Should Never Diet Again.

The myth is that people who are fat have bad or weak willpower, and people who are thin have good willpower, and that’s why they’re thin,” said Mann. “The myth is that you can get thin if you have strong willpower, and you can’t get thin if you have less willpower. Basically, willpower is the thing everyone blames — it’s the first thing people think of and the first thing people toss at dieters when the weight comes back on.”

For example, Mann points to a study (one of 26 her research assistants were able to dig up that focused specifically on food and self-control) in which researchers first had study volunteers complete a questionnaire designed to measure willpower, and then tempted them with potato chips — but asked them to try their best to refrain from eating them. They wanted to see whether the volunteers who’d scored higher in self-control would be better at resisting the chips than those who’d scored lower, but that’s not what they found. Self-control didn’t have much of an effect one way or another on whether or not the volunteers were able to keep themselves from gobbling up the chips.

The problem is that in the context of healthy eating, a one-time lapse in self-control with regard to healthy eating torpedoes your previous, successful efforts at resisting, in a way that just isn’t true in other contexts where self-control does seem to be more highly correlated with success. “Imagine you’re in a meeting and someone plops a big box of doughnuts on the table,” Mann said. “To resist this doughnut, it’s not a one-time thing. You resist it when you first notice it, and you resist it every time you look up and see it again. I know I’d be tempted every time I looked up!” Resisting the doughnut, in other words, requires not just one act of self-control, but many — not to mention that each time you resist, it gets a little more difficult to do so, as self-control is thought to be a limited resource. “So let’s say you resisted it 19 times — which is amazing! That’s some solid willpower. But the 20th time, you’re distracted, you cave,” she continued. “Nineteen out of 20 times in almost any other context is great. But once you eat that doughnut, you get no credit for the 19 out of 20 times you resisted it.”

Despite your valiant efforts, you’ve now consumed exactly the same amounts of sugar, fat, carbs, and calories as you would have if you’d eaten it the first time you were tempted. You may as well have given in then.

Compare that to, say, a student who’s studying for an upcoming test. “The thing you have to control if you’re studying is paying attention to your work rather than stopping and doing something more fun,” Mann said. “So you’re working, but then you have a moment of weakness, and you put down your studying and you get on YouTube.” So you do lose 10, 20 minutes of study time to cat videos, “but everything you’ve studied up until then — it’s still there. It’s not ruined.”

And academic performance does indeed appear to be an area in which higher self-control helps. In a recent review of 102 studies on self-control, Denise T.D. de Ridder of Utrecht University examined, among other things, the predictive powers of the so-called Marshmallow Test — the famous experiment by Stanford social psychologist Walter Mischel that stuck preschoolers alone in a room with a tempting treat (sometimes, but not always, a marshmallow). If they could resist gobbling up the snack before the experimenter came back, they’d get two. De Ridder and her team found that 32 percent of the variance in these kids’ SAT scores more than a decade later could be predicted by whether they were able to resist the marshmallow in the experiment when they were small. She found a correlation between success on the marshmallow test and healthier weight, too, but a much smaller one: Just 4 percent of the variance in weight could be attributed to the willpower the kids exhibited when resisting the treat. “The marshmallow test is eight times stronger in predicting SAT scores than predicting weight,” as Mann explained it.

So it’s true that self-control does make some difference when it comes to weight loss, and it’s also certainly true that people vary in their ability to exert self-control. But in the context of weight and healthy eating, these differences aren’t as important as much as most people might think. “It’s not to say that personal behavior isn’t important — of course it is,” said Rebecca Puhl, deputy director at the University of Connecticut’s Rudd Center for Food Policy and Obesity. “But I think the way to think about this is that obesity is a very complex puzzle and personal behavior is just one of those pieces.”

Last week, Puhl published new research in the International Journal of Obesity that offers a reminder about why believing that willpower is the key component to weight loss is a serious problem. In questionnaires designed to measure the weight bias held by 2,866 people from four different countries (Canada, Iceland, Australia, and the U.S.), Puhl found that when people believed the cause of obesity was lack of willpower, they expressed stronger weight bias, on average, than those who believed biological or environmental factors played the bigger role.

And weight stigma has some unfortunate implications for those on the receiving end of it. The belief that overweight people are lazy or unable to control themselves can lead to fewer job or academic opportunities for overweight people; one brain scan study even showed that some people’s anti-fat attitudes run so deep that when study volunteers watched a video depicting a fat person in pain, the areas of their brains associated with empathy showed less activity than when people watched a similar video showing a thinner person in pain. “I think one of the reasons we see such pervasive weight bias is we have this widespread perception that obesity is the cause of lack of willpower and personal control,” Puhl said. “And that’s an oversimplification — it’s a much more complex condition … and it has much more to do with human biology than personal willpower.”

A better way to think about willpower in terms of eating, Mann argues, is to arrange your life so that you don’t need any of it. Researchers like Cornell University’s Brian Wansink have uncovered some clever ways to reconfigure your environment so that you end up eating less without thinking about it: for example, things like using smaller plates, or refraining from eating directly out of the box or package, are easy to do and have been shown to be effective in helping to curb mindless overeating.

Mann has been thinking about the willpower myth recently, and not just because her book has just come out. Every time she’s seen reports of Jeb Bush’s adherence to the Paleo diet, she says, “it gets me thinking about Bill Clinton, who is in that tiny minority of successful dieters,” in that he’s managed to not only lose weight but keep it off for a prolonged period of time. “I love him but … no one has ever accused that man of having good self-control.”