We all know that the number on the scale isn’t suppose to define us, but that doesn’t stop us from thinking about how much we weigh on any given day. And the number often influences our mood.

So how often should we weigh? Every day, once a week, once a month? The answer depends on your goal–to maintain, lose, or to work on developing a healthy relationship with food.

When to weigh: The best time is right when you wake up. You’ve been resting all night without any hydration or extra calories, so the morning weight should be the most consistent and typically the lowest. And Wednesday is a good day as it is midweek, not right after the weekend where heavier consumption may occur.

How often? If you look at the obesity research, the recommendation is usually to weigh once a week. Keeping track of your food and triggers and then evaluating yourself once a week on a scale usually works to keep weight in line.

To lose weight. The recommendation is to weigh about three times a week. In my book, Lose it For Life, we looked at the National Weight Control Registry, which tracks more than 10,000 people in the U.S. who have lost and kept off significant weight for long periods. Those people tend to weigh regularly which seems a bit counterintuitive. The reason is that regular weigh ins help you accurately track weight loss. You can see if you are losing, need to cut out a few more calories, or make adjustments. And a little gain doesn’t go unnoticed until it is 10 pounds. Regular weighing is good feedback for your weight loss plan.

If you have an eating disorder: Jumping on the scales regularly is not a good idea. In fact, we try to discourage daily weighings unless you are in a hospital having your food prescribed through a refeeding program. Your body naturally fluctuates in weight so daily weigh ins can be discouraging. In addition, daily weigh ins tend to reinforce obsession with the weight number rather than focusing on healthy eating habits.

How often you weigh then depends on your goal. To maintain, weekly. To lose and stay on top of your efforts, two to three times weekly. To treat an eating disorder, work with your therapist. Your goal is to become less number focused and more healthy eating focused.