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 work on developing a healthy relationship with food and not defining yourself by a number.

When to weigh: The best time is right when you wake up. You’ve been resting all night, no 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. Keep track of your food and eating triggers and then evaluate yourself once a week on a scale 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 three times a week. The reason is to get handle on how their eating habits are tracking with weight loss. You can see if you are losing or need to cut out a few more calories, etc. It’s 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 discourage daily weighings unless you are in a hospital getting your food prescribed. 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 you on healthy eating habits.