How to read your weight trend line (the seven-day average)
Your weight jumps up and down each day from water, salt and food in transit, so one morning tells you almost nothing. The honest signal is your seven-day average, the smooth line that shows where your body is really going.
Monday you weigh 72.0 kg. Tuesday jumps to 72.6. Wednesday drops to 71.8. Up, down, up. Which number is the real you? None of them, alone. Each morning's weight is mostly water, salt and food moving through you. The honest signal is one smooth line called the seven-day average. This short read shows you how to read it.
Why one morning lies by about half a kilo
Your body holds water like a sponge. A salty meal pulls water in. Food still in your gut has real weight. Your monthly cycle adds water too. In a long study, day-to-day body mass swung by about 0.4 kg in healthy young men. For a 70 kg adult that is roughly half a kilo either way. That swing is bigger than the fat you can lose in days. So one morning's number is mostly noise.
How to turn seven days into one honest dot
A moving average is simple maths. You add seven days of weight, then divide by seven. That one calm number is your trend dot. Scientists use this same trick on weight data to quiet the daily noise. Here are the four steps.
Read the slope: flat, falling or rising
Now read the shape of your trend dots over two to three weeks. The maths of weight is slow. A daily gap of about 25 kcal between your food and your burn settles into about 1 kg of body change over a long time. Half of that change takes about a year. So the line moves gently. Read its direction, not one single day. Your daily maths is food calories minus (BMR plus active calories). The slope shows whether that gap is working.
The seven-day average hides real weight gain, so it is risky.
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Some worry the average smooths away a true gain. It does smooth the water noise, but it does not hide a real trend. If you are truly gaining, the line bends upward within two to three weeks. The average only removes the fake panic of one salty dinner. You still see the truth, only calmer. Burnie logs your weight for free and draws this line for you. It never reads your heart rate, sleep or location.
The bottom line
Single days lie by about half a kilo. The seven-day average tells the truth. Plot one calm dot each week, then read the slope. Flat means matched, falling means your deficit is working, rising means eat a little less. Burnie tracks your weight and your daily deficit for free, with no heart-rate, sleep or location reading. Watch the line, not the dot.