If you weigh in every morning, you've probably seen the scale jump a pound or two overnight, sometimes in the "wrong" direction right after a great day. That's normal, and almost none of it is fat. This article explains why your scale weight bounces around, what your trend weight is, and why MacrosFirst relies on it to measure your progress and your expenditure.
Your body weight includes much more than fat and muscle, and most of the rest changes from day to day.
The biggest factor is water. A salty meal makes your body hold on to more water, and so can hot weather, poor sleep, stress, and the menstrual cycle. Hard or new workouts do it too, since muscles hold extra water while they recover. Carbs play a part as well: your body stores carbs together with water, so a higher-carb day can show up as extra weight the next morning, and a low-carb day can make the scale drop quickly. Then there's simply the food and drink still working its way through your system.
Together, these can easily move the scale 1 to 3 lb (0.5 to 1.5 kg) from one day to the next. That's far more than real fat change: gaining even a single pound of fat in a day would take eating thousands of calories more than you burn. So when the scale jumps overnight, it's almost always water and food, not fat.
To see past that noise, MacrosFirst smooths your weigh-ins into a trend weight. It's a moving average that leans on your most recent weigh-ins, so it follows real changes over days and weeks while filtering out the day-to-day bounce. A single unusual weigh-in barely moves it, and an obviously mistaken entry can't throw it off much.
You can see both lines on your Weight chart. From your Dashboard, tap the Weight chart, then tap Scale Weight or Trend Weight at the top to show or hide each one. Once you've logged at least 5 weigh-ins in the last 14 days, the chart also projects where your weight is heading if your current trend continues. For more on logging weight and using the chart, see Body Weight.
MacrosFirst learns your expenditure by comparing what you eat with how your weight changes. If it used raw scale weight, one salty dinner could look like your metabolism suddenly slowed down, and one dehydrated morning could look like a breakthrough. Your trend weight lets it respond to real changes in your body instead of to water and food. See Energy Expenditure: How MacrosFirst Measures What You Burn.
The same goes for you. When you're judging your own progress, the trend over a couple of weeks tells you far more than any single morning on the scale.
Weigh in under the same conditions each time. First thing in the morning, after using the bathroom and before eating or drinking, works best.
Weigh in often. Daily or most days gives you the smoothest, most accurate trend. MacrosFirst needs at least 2 weigh-ins in the past 14 days to keep updating your expenditure, but more is better.
If you use a smart scale, connect it through Apple Health or Google Health Connect so your weigh-ins import automatically. If your scale records more than one weigh-in in a day, MacrosFirst imports the lowest one.
Don't react to a single weigh-in. Give it a week or two and look at the trend.
Your trend weight is one of the two signals behind everything MacrosFirst calculates. These articles show how it's used:
"How does MacrosFirst measure what I burn?" Energy Expenditure
"How much do I need to weigh in?" What Data MacrosFirst Needs
"How do I log my weight or use the Weight chart?" Body Weight
Why does progress slow down over time, and what does MacrosFirst do about it? Now that you know how to read your weight, the next step is understanding how the gap between what you eat and what you burn drives your progress: Energy Balance: Why Progress Slows and How MacrosFirst Adapts.
