So for the first couple of days, measure out the foods you typically eat with measuring spoons and cups to get a better feel for your portion sizes. When you guestimate, it's easy to get confused when your calories appear to be right on track but your weight stays the same. Although the default entry for a serving of cereal, for example, is a half cup, most of us eat about two cups. “I see this with my clients all the time,” says Brissette. And if you’re eyeballing it, you may underestimate portions. MyFitnessPal only works if your input is accurate. Here are the MyFitnessPal fails that could be sabotaging your weight loss.

In fact, some mistakes could push you further from your goal.

That said, using the app to lose weight isn’t foolproof. Tracking your meals-whether in a journal or an app-helps you eat less because it increases your awareness of what you put in your mouth. MyFitnessPal can be a genius weight loss tool-especially if you have a tendency to munch mindlessly or have no idea how many calories you’re eating in the first place, says Christy Brissette, R.D., president of 80 Twenty Nutrition.

Myfitnesspal calorie burn calculator