We separate fact from fat fiction with the real info you need to keep pounds off.

By Jessica Migala

Another day, another box of doughnuts at the office, another pizza at your PTA meeting, another plate of nachos with the kids. When you're trying to slim down, it can seem like the whole world is dishing up something delicious to eat — along with a side order of not-so-savory advice, such as "You'll work it off at the gym!" Don't let bad suggestions ruin your good intentions. Instead, learn what really gets results with our guide to dieting in a happier, healthier and more successful way.

Myth: One slip-up means you might as well start over tomorrow

Why It Backfires: If you throw your hands in the air and say "My diet's ruined now" (also known as the what-the-heck effect), you'll do it again at the next meal and the next, and then the scale will start creeping upward. Blowing your entire calorie budget for lunch on just the appetizer isn't license to get another round of rolls for the table and the molten chocolate lava cake for dessert. "Life throws us curveballs," says Lauren Schmitt, RD, a Los Angeles-based registered dietitian. "No eating plan will be flawless, and it doesn't need to be."

Smarter Strategy: If you eat something unhealthy, use that as motivation to pull a 180. Ask yourself, "What one thing can I do right now to get back on track?" Maybe you double up on veggies in your main course or substitute a whole grain like quinoa for the fries you were about to indulge in. Then consider how you can start tomorrow off right. When Christina DiPierro, 38, of New York City, falls off the wagon, she writes down two small health goals for the next day, like eating a serving of fruit in the morning or working out for 30 minutes. That's not compensating, that's a healthy reboot. And when you write down your goal — and commit to it — you can rest easy knowing you've got better times ahead.

Myth: You can exercise away that second slice of pizza

Why It Backfires: It's way easier to eat calories than to burn them. For example, a slice of pepperoni pizza has about 300 calories and a large blueberry muffin has around 500. While they may take you five minutes to eat, you'd have to cycle briskly for about 35 minutes to pedal away that pizza — and an hour for that muffin. Plus, data shows we tend to think we're reaping greater benefits than we really are. The calorie counter on your gym's elliptical is just an estimate, one that could be off by as much as 42 percent.

Smarter Strategy: Schedule your sweat session before, not after, an indulgence. In one study, people who went for a run prior to hitting a buffet netted nearly 500 fewer calories compared to a group that rested before chowing down. That's partly because the jog gave them a calorie deficit and partly because it reduced their appetite. An added bonus: When you think that exercise is enjoyable — rather than viewing it as a chore, like cleaning the oven — you're far less inclined to go overboard with treats after being active, according to research. So whether it's a bike ride or a barre class, find something to do that makes you happy. "I used to hate the word 'workout,' so I tried to trick myself into doing things that are fun, like racing my children outside or turning on a song that I know gets the kids grooving so we dance for half an hour," says 43-year-old Dawn Alexis Anderson of Dover, Delaware.

Myth: If you're going to a party tonight, save calories by skipping a meal

Why It Backfires: "Pass on lunch and you'll arrive at the party so hungry that you'll find it hard to stick to a healthy diet," says Erin Palinski-Wade, RD, author of Belly Fat for Dummies. Plus a Cornell University study found that when people fasted for 18 hours (think: not having breakfast) they chose more carb- and protein-heavy foods over veggies at their next meal. When your body thinks it's starving, it primes you to want the fastest, most efficient sources of calories. And that's chicken and cheese — not carrots.

Smarter Strategy: It's possible to "bank" calories for your favorite party foods by eating 100 fewer calories at each meal during the day. Make easy swaps: Use skim milk and cinnamon in your coffee instead of cream and sugar, leave the cheese off your sandwich, and have sliced cucumbers and carrots dipped in salsa instead of pita chips. Then eat a 150-calorie protein-rich snack two hours before you go out. Tanee Janusz, 35, of New Orleans, has apple slices with a smear of peanut butter to beat the buffet table munchies. It's a winning combo of three hunger-busting nutrients: fiber, fat and protein. Other ideas: a light mini Babybel cheese and whole-grain crackers or a piece of whole wheat bread with a couple slices of deli turkey and mustard, says Bonnie Taub-Dix, RDN, author of Read It Before You Eat It.

Myth: Just be strong and ignore the brownies, cookies and cakes

Why It Backfires: Willpower is like a muscle, says Darya Rose, PhD, author of Foodist. All types of events (like trudging through your day on five hours of sleep or having to wait in an extraordinarily long line at the supermarket) tire it out, leaving you with less and less ability to resist temptation as the day goes on. Now you know why chips look even more alluring when your kids are screaming.

Smarter Strategy: Don't "ban" a particular food from your diet, says Rose. Instead, tell yourself it's off-limits for now and that you can have it at some other point. In one experiment, students who knew they could have potato chips at a later time ate fewer of them than those who were given permission to eat the chips or asked to avoid them entirely. Shoring up your willpower also helps with this delayed gratification. Rose suggests getting plenty of rest, catching a few minutes of solitude and enjoying a small, healthy sweet treat like fruit. Low blood sugar tells your body you need to eat (and eat now!), but the fruit will keep your levels steady and prevent cravings.

Originally published in the April 2015 issue of Family Circle magazine.