Oct. 22, 2025 – Eat healthier. Exercise more. Take your medication. Quit smoking. Chances are, everyone you know has made a health vow like this.
Chances are even better they failed.
“Setting long-term goals is a uniquely human trait,” said Elliot Berkman, PhD, a professor of psychology at the University of Oregon who studies health behaviors. “Yet, paradoxically, we are really quite bad at achieving them.”
New Year’s Resolutions are routinely abandoned. At least 80% of diets fail. Smokers try as many as 30 times before kicking the habit. And in what some call an “ignored epidemic of medication nonadherence,” up to half of chronic disease patients either don’t take their prescribed drugs as directed or don’t take them at all.
“If nonadherence were listed as a cause of death, it would be around the sixth most common cause in the United States, killing about 125,000 people annually (that’s more than Alzheimer’s),” said Fred Kleinsinger, MD, a family practice doctor in California who has researched the subject. “Millions of people are dying, and billions of health care dollars are being wasted because people don’t take their damn medications.”
It’s enough to make you wonder: Why do rational people, with good intentions, consistently not do what’s right for their own health?
Over the decades, psychologists have blamed everything from lack of information to scarce resources to weak willpower. But mounting evidence suggests a deeper challenge: Our brains are working against us.
“We evolved to be highly sensitive to learn where we receive rewards and work hard to recreate the situations that brought them about,” said Berkman, who uses brain imaging to study why people fail and succeed at health goals. “Attempting to change behaviors ... often means working against this powerful system.”
The good news: Now that we’re learning how the system works, we’re also discovering ways to coax it to work in our favor.
Knowledge and Willpower Are Not Enough
For decades, public health campaigns assumed that if people just knew what was good for them, they’d do it. That hasn’t proven to be the case.
Take the “5 A Day for Better Health Program.” Launched in the 1990s, the ambitious national marketing campaign urged people to eat five servings of fruits and vegetables a day to help prevent cancer and heart disease.
Before that, only 8% of Americans knew of this science-backed advice. Six years later, after TV ads, radio jingles, and grocery store signs saturated the country, that number had jumped to nearly 40%. It was a huge marketing success.
Yet, to this day, only about 11% of Americans actually eat five servings of produce daily – a figure that’s barely budged since the 1980s.
“So often we’ve already got the right attitudes and beliefs and knowledge, but it doesn’t translate into behavior change,” said Wendy Wood, PhD, provost professor emerita of psychology and business at the University of Southern California and author of Good Habits, Bad Habits: The Science of Making Positive Changes that Stick.
Motivational experts have long glorified willpower as the key to success. Scientists used to think willpower was like a muscle – some people had more of it than others, and it could wear out over time. Others theorized that low blood sugar, like an empty gas tank, affected brain regions involved in decision-making, leading people to succumb to unhealthy temptations.
“That turned out not to be true at all,” Berkman said. Engaging your willpower uses about as much glucose in the brain as daydreaming does – not much.
What makes change so hard?
“What we’re up against, really, is habit,” Berkman said.
Your ‘Second Self’ Is Often in Charge
Almost half of your life is run by habits.
From the moment you wake up in the morning to the time your head hits the pillow at night, you perform about 43% of your actions without consciously doing so – often while thinking of something else, according to Wood’s research.
“Think of it as a kind of second self,” Wood said.
These habits serve us well, providing “shortcuts in our brain” that help us automate things we’ve learned, through repetition, bring us reward. After the first few times we drive a car, we no longer think about turning the key, easing off the brake, and hitting the gas. When we brush our teeth, we put little thought into spreading the toothpaste across the bristles.
Brain imaging studies suggest these neural shortcuts operate in one region of the brain, freeing up others for more complex endeavors.
The problem: Unhealthy habits are as stuck in our brains as healthy ones. “The exact same mechanisms are at work,” Wood said.
According to neuroscientist Marcus Stephenson-Jones, PhD, that mechanism goes something like this:
When we do something rewarding for the first time – say, pouring a glass of wine in the kitchen after work – we use the conscious, decision-making parts of our brain. If we like it, a puff of dopamine is released in an ancient part of our midbrain – a signal that says, essentially, “I like that. Do it again.”
Once we repeat the task several times, a different area of the brain – one that’s about movement and sensation rather than values – takes over, lighting up in anticipation every time we experience that same cue (the bottle of wine on the counter at the end of the workday).
We have rewired our brain. We have made a habit.
This neural circuit moves fast, nudging us to act before our rational brain has time to intervene. That’s helpful when the habit is going to the gym or slipping on our CPAP each night, but not so much when it’s Dry January and the habit is drinking a nightly glass of wine.
Animal studies show that even after the initial reward wears off, habits persist. Rats habituated to press a bar for food pellets will keep pressing even when the food stops. People eat junk food, or smoke or gamble, even when it no longer feels good.
“It’s like a copying system,” said Stephenson-Jones, who studies the neural mechanisms of habit formation at Sainsbury Wellcome Centre in London and led a May study in Nature that shed new light on the process. “Initially, we set up our goals and preferences based on things we like, and then if we do it often enough, it is stored in this other system in the brain. Once it’s copied there, that’s a habit and it is incredibly resistant to changes in our new preferences and goals because it literally has no idea what they are.”
How to Break, or Make, a Habit
The key to sustaining positive behavior change is to get the system to work for us instead of against us, said Wood.
That means focusing on three things: cues, obstacles (a.k.a. “friction”), and alternatives.
When trying to ditch a bad health habit, remove cues and add obstacles, she said. And adopt new, rewarding habits to drown out the noise of the old.
Trying to cut back on junk food? Lock the candy bowl away and replace it with fresh fruit. Or map a new route from work that avoids McDonald’s and passes a scenic park instead.
Forming new healthy habits requires the reverse: We must add cues to remind us and reduce friction between us and our goals. That could mean choosing a gym closer to home. Or it could mean placing your blood pressure medication next to your toothbrush, enabling a new healthy habit to piggy-back off an established one.
Wood points to government antismoking campaigns as a perfect example of how this can work on a large scale.
In the 1950s, nearly half the U.S. population smoked cigarettes. Even after the 1964 Surgeon General report revealed that tobacco was the leading cause of preventable death in the United States, 40% still lit up regularly in the 1970s.
“But then the government removed the cues and added friction,” Wood said.
New policies mandated that cigarettes be taken off store shelves and locked behind counters, TV ads were outlawed, smoking was banned in public places, and heavy taxes were levied on cigarettes. Smoking became a hassle, and the habitual ruts carved into the brains of thousands of Americans began to fade.
Today, only about 15% of Americans smoke cigarettes.
“It was an astounding success,” said Wood. “It proves that we can change people’s behavior.”
Where Motivation Comes From
Habits aside, the more rational, conscious parts of our brain do play an important role in all this. They are, after all, where the motivation to change begins.
“Anyone can put on their sleep apnea machine once,” Berkman said. “Or take the pill with the unpleasant side effects once. Or exercise once. How do you motivate people in a way that is sustained?”
Some studies show cash rewards can work in the short term, but long-term success comes from aligning your goal with your identity. Don’t just plan to stop smoking – commit to being a nonsmoker, said Berkman. Don’t set out to start running – set out to become a runner.
“If you can think about the behavior as reinforcing the kind of person you want to be, that’s really powerful,” he said. “And you don’t run out of that kind of currency.”
Research suggests that having a clearly defined “why” – to be around for your daughter’s wedding, or see your grandchild’s first soccer game – can also help. One study found that while education alone did little to encourage breast cancer patients to take their medication, what did work was having them identify their why, write it on a sticker, and stick it – along with a photo – on their pill box.
Peer support is another key. Studies consistently show that people who try to quit smoking are far more likely to fail if their partner also smokes. On the flip side, having just one person working alongside you on the same health goal can help. A study from the University of Arizona Health Sciences Center found that people with sleep apnea were much more likely to use their CPAP machine – a lifesaving therapy with notoriously terrible adherence rates – when peer mentors who also used them visited regularly.
Advances in medicine and technology are aiming to help too. Weight loss drugs quiet the “food noise” in patients’ heads. Apps remind people to work out or take their medicine. And someday soon, a sleep apnea pill could replace that cumbersome CPAP.
But whether those tech fixes can work in the long term remains uncertain. For now, your best bet is to enlist your second self, said Wood. That takes repetition. According to one study, people must repeat a simple health behavior for 66 days before it feels automatic.
In the end, brain networks are malleable – and persistence pays.
“People tend to get discouraged easily and give up, which is understandable,” said Berkman. “They need to appreciate how hard this is. You’re up against really powerful evolutionary systems. So give yourself some grace and keep trying. In the end, it is possible to change.”
