Your change rate is based on changes in your trend weight over the past 20 days, expressed as a weekly figure. We use this figure to estimate the size of the caloric deficit or surplus you've been in. When we combine that information with data regarding your energy intake over the same time span, we can estimate your daily energy expenditure, thereby allowing us to update your weekly calorie targets to keep you on track with your goals.
We focus on changes in trend weight for this calculation, rather than changes in scale weight, because trend weight is less influenced by outlier weigh-ins. This allows us to make more gradual changes to calorie and macro targets week-to-week to keep you on track toward your goals. More importantly, it lets us avoid situations where short-term fluctuations in scale weight would imply the need for unnecessarily large increases or decreases of calorie targets.