Beware: Food frenemies are everywhere. In fact, research shows that if you eat with another person, you'll down 33% more on average. Here’s how to enjoy the company, without the calories.

Your partner

Because of what scientists call your “shared environment,” your chance of becoming obese is 37% greater if your significant other is heavy. “There has to be teamwork,” says Cynthia Sass, RD, Health's contributing nutrition editor. “That might mean putting food in separate his-and-hers cabinets.” When dining with the brood, leave family-size platters in the kitchen and let everyone help themselves. You can control your own portions and avoid temptation in the form of second helpings.

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Your kids

One study found that moms consumed almost 400 calories more a day than women without children. Be prepared: If it’s after-school-snack time, have your own healthy treat ready (maybe a handful of almonds with Greek yogurt). At mealtime, divide and conquer: Put your chicken breast over steamed vegetables, theirs over cheesy pasta. Everyone eats well!

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Your BFF

Check this out: Your chance of becoming obese increases by 57% if one of your close friends is heavy, according to research. If you’re going out for a quick bite, tell your bud that you plan to order something healthy—or offer to split an entrée and add a salad. A study at Arizona State University showed that most friends are “monkey see, monkey do”: In other words, if you take the lead, your pal is likely to follow suit.

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Your co-workers

Those out-of-office lunch trips can be great for camaraderie but deadly for your diet. According to a study from Georgia State University, if you dine with a group of seven or more people, you will eat a staggering 96% more. Your best weapon is strategic planning. “Scan the menu ahead of time,” recommends Rachel Beller, RD, author of Eat to Lose, Eat to Win.

“When the waiter comes over to the table, say, ‘I want a simple piece of grilled salmon, with sauce on the side, and a double order of vegetables, in light oil or steamed.’ If I’m in the mood for a real flavor punch—let’s say I’m at an Italian restaurant—I’ll ask for a small side of marinara sauce, which I pour over my veggies. You had better believe that everyone else at the table will be eating off my plate!”

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