Going out to dinner is a great way to get out of the house, spend time with friends—and not have to cook or clean up. But when you’re trying to eat healthfully, watch your portion sizes and avoid overdoing it, eating at restaurants can be tricky. The menu doesn’t usually tell you how many calories are in a dish, or whether it was cooked in fatty butter or omega-9-packed olive oil. And it’s full of temptations like fried foods and delectable desserts you’d never be able to make at home. People have been shown to eat more when dining out with a group—and the larger the group, the bigger the difference. Eating with one other person increases consumption 28 percent over eating alone. Table for six? That leads to a 71 percent jump.So how can you dine out without a side order of regret? New research suggests the answer: Go to dinner with a like-minded friend. The study findings, presented at the 2013 annual meeting of the Agricultural and Applied Economic Association, show that people tend to order like the others in their dining party. Hearing your friends choose healthy, lower-calorie options makes you want to choose healthy, lower-calorie options. It’s a form of peer support.QUIZ: What’s Your Eating Style?The lead researcher on the study, University of Illinois food economist Brenna Ellison, says that people were happier with their choices if they were similar to what everyone else was eating—even if they weren’t exactly psyched to order a salad or healthy entrée in the first place. Her conclusion? Healthy friends lead to healthy dinners and happier diners.Here are four other ways to put some order back into your ordering:1. Decide before you dine. Most restaurants have online menus. After lunch (when you’re already full), check out the website and pick the best option for dinner. That way you won’t cave to in-the-moment cravings.2. Order first. Nobody wants to be the lame duck ordering grilled vegetables with brown rice after everyone else has settled on creamy pastas and burgers. Nip the situation in the bud by being the first person at the table to order. You might even make your companions rethink their indulgent menu picks.3. Pay attention to portions. Restaurant portions are often bigger than anything you’d serve yourself at home. (And they’ve been growing for years.) If you find yourself getting full when you’re halfway through, ask the server to pack the rest up to go. Then, you won’t overstuff yourself by picking, and you get an extra meal out of it. Who said there was no such thing as free lunch (the next day)?MORE: Design a “Skinny Kitchen”4. Refuse refills. They’re a good deal for your wallet—but a bad bet for your belly. In one study, people ate 73 percent more soup when the bowl was secretly refilled as they slurped. As much as you’d like another complimentary basket of bread or another drink, a polite “no thanks,” is the way to go. We promise, the waiter won’t be offended.