It's a common slipup: After weeks of eating well, hitting the gym, and skipping dessert, you're on track to lose those five pounds. You deserve a reward—some candy, a (non-diet) soda, or a side of fries. But hours later, the scene around you looks like The Hangover meets the Food Network.
In the same way that some drugs pave the way for even harder ones, a weakness for a certain foods can open the door to an avalanche of bad eating choices, says Gary Wenk, Ph.D., author of Your Brain on Food. Some foods are like gateway drugs," he says. "From your brain's viewpoint, there is no difference." These so-called gateway or trigger foods make you feel out of control, maybe even physically unable to stop reaching for more, in part because of their addictive effect on your mind and body, according to research. But rehab is probably easier than you think.
Junk Food Junkies
It may seem silly to think about being addicted to food, something we'd die without, but most of us eat for a lot more than just survival. Merely looking at or thinking about a food you know you love activates the reward portion of your brain, the nucleus accumbens—the same area stimulated by drugs and alcohol. This triggers the release of dopamine, a feel-good chemical that enhances your awareness of that food (so forget ignoring it!).
And once you've taken that first bite, watch out. Tasting food engages all of your senses (and may be felt more intensely in women than in men, for unknown reasons). Your nervous system responds by secreting insulin (which drops blood glucose) and relaxing your stomach muscles, which makes you feel like you need to eat more to be satisfied, says Susan Roberts, Ph.D., a professor of nutrition at Tufts University and coauthor of The "I" Diet.
There's a reason this tends to happen almost exclusively with fatty and sugary foods and not, say, lettuce. The saturated fats in foods like bacon and cheese impair your brain's normal ability to regulate appetite and cravings, so you don't realize you're full until you're completely stuffed, says Kelly McGonigal, Ph.D., a health psychologist at Stanford University and author of The Willpower Instinct. What's more, that effect on your appetite can last for up to three days, the length of time it takes to flush those fats from your system. So one unhealthy indulgence can end up triggering a major relapse.
Add sugar to the fatty food—ice cream, cake, doughnuts—and you have a double whammy. High-sugar foods increase your levels of ghrelin, a hormone that stimulates appetite and increases cravings. "So you may tell yourself 'Just one bite' but find yourself wanting more and more, the more you eat," says McGonigal.
Sugar also has been shown to enhance memory storage, which may explain why you want it in the first place, and so much of it on special social occasions. As a result, your brain has evolved a system of rewards that gives you a real high when you eat sugar. "The brain responds to both sugar and fat by releasing endorphins," says Wenk. Chemically, those feel-good compounds are similar to morphine and can have a biological impact similar to a shot of heroin—including causing you to jones for another fix when the initial euphoria begins to fade.
RELATED: 13 Ways to Fight Sugar Cravings
Avoiding cravings entirely is tough, given that they can be brought on by stress, PMS, or even just thinking about eating. But there's plenty you can do to avoid skidding down the slippery slope of gateway foods.
Use Your Head
One of the best times to stop a binge is before it begins.
A 2010 study by Australian researchers found that thinking about a craving uses up mental energy—enough that you'll struggle to do anything else or even think normally. But if your brain is otherwise engaged, you'll have fewer cognitive resources available to conjure up mental images of brownies. So when a craving hits, try doing long division, sudoku, or counting backward, and see if it goes away.
If you're three bites into a pint of fudge ripple when you feel a pang of regret, try switching to a healthier snack. Once your senses have been engaged, your body is going to demand more food, but you can still decide what to give it. Sorbet or a piece of fruit can freshen up your palate, which can help put the brakes on thinking about the stuff you crave.
Hide Your Triggers
Proximity to food influences how much of it you eat, says James Painter, R.D., a professor at Eastern Illinois University who studies behavioral eating. Try keeping healthy foods right where you can see them, and stash unhealthy ones in a hard-to-reach drawer—or just don't keep them around at all.
Get Back On Track
Maybe you couldn't stop yourself from polishing off the entire caramel sundae, but that's no reason to give up entirely. We have a tendency to focus on the short-term consequences of our actions, but keeping a long-term goal in mind—say, fitting into that really cute bikini—can help you realize that you can still get there despite a setback, says McGonigal. Think of it this way: Every meal is a chance to start over and do it right.