During the holidays, you want to spare yourself the strictness of a typical healthy eating plan. You allow indulgences and missed workouts to pile up a bit more than you should. That extra five pounds you've gained? Eh, you chalk it up to bulking season. But come New Year's day—just one short week after the gluttony ebbs—you put your body through the ringer: two-a-day workouts, juice cleanses, pantry sweeps. It's too much.

Sure, you probably get the scale to budge in your favor. But if your body could talk it would probably scream What are you doing to me!? Well, quite a lot, actually. And close to none of it's good—especially if yo-yo dieting is a yearly (if not monthly) trend for you.

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Side Effects of Yo-Yo Dieting

Weight Gain

A new study from the University of Exeter and Bristol found repeated dieting can do the opposite of what you want and ultimately lead to weight gain because your brain interprets these extreme swings in eating patterns as "short famines." (Which is different than calculated fasts.) You can probably guess where this is going. Your body goes into survial mode and prompts the storage of fat for future shortages. This is also a common downfall for people who try to stick to super low-calorie diets. What's more, you're more apt to binge and overeat, so you're never truly able to keep any weight off. You can thank evolution; animals, like birds, respond to shortages in food supply by gaining weight to stay alive. Unfortunately, the researchers say, our bodies are hardwired to follow this model.   

"Surprisingly, our model predicts that the average weight gain for dieters will actually be greater than those who never diet," leady study author Andrew Higginson said in a press release. "This happens because non-dieters learn that the food supply is reliable so there is less need for the insurance of fat stores."

Gut Punch

That gargantuan shift from hot wing-stuffing-cocktail binges to I'm-only-going-to-eat-negative-calorie-celery benders you transition in and out of from the onset of football season to New Years is a rough one—especially for your stomach, according to a study from the University of New South Wales. And we don't just mean when it comes to your waistline. Yo-yo dieting throws off the healthy balance of gut bacteria. Usually, your gut's home to about 100 trillion microbial cells that influence everything from metabolism to immune function to overall nutrition. But when the levels and diversity of bacteria are disrupted, gastrointestinal conditions like inflammatory bowel disease and obesity are the result. 

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Psychological Frustration

By depriving yourself of fuel and maxing out during workouts, your only result is burnout. Sure, you'll see some weight loss; but that's only due to water loss and dehydration. "When people put themselves on a diet, they often forbid themselves to eat the foods they love, but dieting is not the same as healthy eating, and this leads to a sense of deprivation, which can derail your healthy intentions," says Rebecca Scritchfield, registered dietitian nutritionist, and health/fitness specialist. "Over time this creates the effect of yo-yo weight cycling, which can take a toll on your emotional and physical well-being," Scritchfield says. See what other weight loss methods nutritionists would never use. 

It's still relatively unclear what exactly the longterm consequences of yo-yo dieting are—and whether or not this weight change fluctuation puts you at greater risk for disease compared to people maintaining obesity, according to research published in the International Journal of Exercise Science. But, still, why not save yourself from the vicious cycle?

Bottom line: "The best thing for weight loss is to take it steady," Higginson says. "Our work suggests that eating only slightly less than you should, all the time, and doing physical exercise is much more likely to help you reach a healthy weight than going on low-calorie diets," he adds.

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