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The only thing more common than fending off a hangover on New Year's Day is resolving to make it the year you finally, finally lose weight. There's only one minor problem with that resolution: You will almost certainly fail to keep the pounds off. Diets don't work — at least not for long.

"It's not that they don't work; it's that they never last," health scholar Tim Caulfield told Fusion.

"If you look at the research accumulating around the world about dieting, it's pretty grim. Almost everyone puts the weight back on," said Caulfield, a professor in the School of Public Health at the University of Alberta. He's also the research director of the Health Law Institute, a Canada research chair in Health Law and Policy, and a senior health scholar for the Alberta Heritage Foundation for Medical Research.

"People will go on a fad diet or commercial diet and pay attention to what they're eating for that period of time, and they'll lose weight. But the problem is that it inevitably comes back on," he said.

Blame it on your brain

A study that came out of the University of Minnesota confirmed what obesity researchers like Caulfield have known for a while: the success of long-term dieting — the abiliity to lose weight and keep it off for 5- 10 years — is close to impossible. Statistically, only about 5 percent of people who lose a significant amount of weight keep it off for years afterward.

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The culprit for the pernicious pound-regaining is your brain. Obesity researchers, including Caulfield, confirm the existence of a "set point" of weight that your brain accepts as OK for your body. It's not really a point, per se, but a range of about 10-15 pounds in which your body will continue to function normally. Once your weight dips below that acceptable range, your brain goes into panic mode. And it does that whether you lose the weight incrementally, through diet and exercise, or with something like liposuction, where a bunch of fat is removed at once.

"Our body, our mind conspire against us to get back to whatever point that is," Caulfield said. "Our bodies are incredibly efficient eating machines. We trick ourselves into eating more. Our bodies aren't designed to lose weight, they're designed to put weight on."

Sandra Aamodt is a neuroscientist and author who gave a TED Talk in 2013 titled "Why dieting doesn't usually work." Several years ago, after decades of cycling from diet to diet and never losing weight for good, she made a New Year's resolution she was able to keep: She gave up dieting. As someone who studied the brain, she knew exactly why she and millions of other Americans struggle to drop weight and keep it off.

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"There are very old and mostly unconscious brain systems whose job is to make sure that you don't lose too much weight," she told Fusion. In her TED Talk, she explained what specifically happens in your brain when you slip below your set point: Your hypothalamus sends signals that affect how hungry you are, your activity level, and your metabolism. She cited research from Columbia University that showed people who had lost 10 percent of their body weight burned 250 - 400 fewer calories per day because their metabolism is suppressed.

A lot of people like to make the argument that, OK, maybe diets don't work, but "lifestyle changes" can lead to substantial long-term weight loss. But while making changes like cutting out soda or fast food or red meat will improve your health, they probably won't drastically change the number on the scale. You might drop a couple pounds, but you'll still be in that set point range.

"If you became a low-fat vegetarian and you're currently an eater of steaks and potatoes, you'll probably lose 10 pounds or so," Aamodt said. "It's extremely unlikely you'd lose 100 pounds that way." She said there are some exceptions — for instance, if someone with a binge eating disorder is able to stop binging. Otherwise, you can shuffle around within your body's accepted weight range, but "lifestyle changes" probably won't get you very far below it.

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Why we all make the same resolution every year

USA.gov lists the most popular resolutions people make. Number one on the list: Lose weight.

Michelle Allison is studying to be a registered dietitian and runs the blog "The Fat Nutritionist." She offered some insight on why everyone simultaneously decides that Jan. 1 is the perfect time to start a diet plan.

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"After you have a time where there's lots of holidays and food and activities surrounding eating, and it's cold outside and you want to do things indoors, it's very normal to say, 'oh God, I want to have salad and go for a walk and have a glass of water,'" Allison told Fusion. "That's a totally normal reaction to planned holiday indulgence. But it's become a thing where people feel obligated (to start a diet)."

What you can do instead

Still, the situation isn't so dire that you should live in your sweatpants in a cave with soft lighting. There are better ways to improve your health than just losing weight, and there are ways to learn to love your body more, even if you don't naturally look like a supermodel.

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Caulfied (the health researcher and professor) listed the five things that everyone can do to improve their health: Quit smoking cigarettes. Exercise. Get a good night's sleep. Develop and maintain relationships with other people, whether they're family, friends, or significant others. Eat so-called "real food" (foods in their natural state, like fruits and vegetables and nuts, and foods made with whole grains, natural sweeteners, and other non-processed ingredients). Everything else people recommend to improve health "is kind of baloney," which, incidentally, is not good for your diet, according to Caulfield.

"People who exercise regularly, people who are fit, tend to be healthy no matter what they weigh," Aamodt said. "There's good evidence that exercise is more important for health in people who are heavier than in people who are thinner. There's a bigger difference between an unfit obese person and a fit obese person than between an unfit thin person and a fit thin person."