Weight Tracking Glossary
Every term you'll meet while tracking your weight — defined in one or two sentences, with the numbers that matter. Linked guides go deeper.
Weight trend
Your weight's direction of movement over one to two weeks, with daily fluctuations smoothed out. The trend — not any single weigh-in — is the most reliable indicator of whether you are actually gaining, losing or maintaining weight, because daily readings can swing 1–2 kg from water and food alone.
Water weight
Temporary weight from retained water rather than fat. Salt, carbohydrates, hormones, heat, stress and hard exercise all change how much water the body holds. Water weight commonly moves the scale 0.5–2 kg and typically clears on its own within 1–3 days.
Weight fluctuation
The normal day-to-day variation in body weight — commonly up to 1–2 kg — caused by water balance, food in transit, sodium, hormones and exercise. Daily fluctuation is noise, not fat: gaining a kilogram of actual fat requires roughly 7,700 surplus calories.
BMI (Body Mass Index)
A screening number calculated as weight in kilograms divided by height in metres squared (kg/m²). For most adults, 18.5–24.9 counts as the healthy range, 25–29.9 as overweight, and 30+ as obesity. BMI cannot distinguish muscle from fat, so muscular people often score 'overweight' at low body fat.
TDEE (Total Daily Energy Expenditure)
The total number of calories your body burns per day: your basal metabolic rate plus all activity, digestion and movement. You lose weight when you consistently eat below your TDEE. It is commonly estimated with the Mifflin-St Jeor equation times an activity factor.
BMR (Basal Metabolic Rate)
The calories your body burns at complete rest just to stay alive — breathing, circulation, cell repair. BMR typically makes up 60–70% of total daily burn and is estimated from sex, age, height and weight.
Calorie deficit
Eating fewer calories than your body burns (below TDEE). A deficit of about 500 kcal per day produces roughly 0.5 kg (1 lb) of weight loss per week, since one kilogram of body fat stores about 7,700 kcal. Deficits below 1,200 kcal/day of total intake (women) or 1,500 (men) are not recommended without medical supervision.
Weight loss plateau
A period of two to three weeks or more where the weight trend is genuinely flat despite continued effort. Shorter flat spells are usually water retention masking fat loss. Real plateaus happen because a lighter body burns fewer calories, shrinking the original deficit.
Goal weight
The target weight a person is working toward. A realistic goal weight sits within the healthy BMI range for your height, allows a sustainable pace of change (0.5–1 kg per week), and is best treated as a range of about ±1 kg rather than one exact number.
Maintenance range
A band of roughly ±1–2 kg around your goal weight used after weight loss. Inside the band, daily wobble is ignored; if the trend sits above the band for about two weeks, a small correction is made. Regular weigh-ins are the strongest predictor of keeping weight off long-term.
Trend line (smoothed weight)
A moving average drawn through daily weigh-ins that filters out day-to-day noise so the underlying direction is visible. Apps like Weightnote, Happy Scale and Libra are built around trend lines rather than raw daily numbers.
Glycogen
The body's stored form of carbohydrate, kept in muscles and liver. Each gram of glycogen binds roughly 3 grams of water — which is why low-carb diets show fast early 'loss' and a pasta night can add 1–2 kg overnight. Both effects are water, not fat.
Ideal weight formulas (Devine, Robinson, Hamwi)
Clinical rules of thumb from the 1960s–80s that estimate an 'ideal' body weight from height and sex, originally for drug dosing. They disagree with each other by several kilos and ignore body composition, so they serve as context rather than targets.
Non-scale victory
Progress that the scale cannot show: looser clothes, smaller waist measurement, better energy, strength gains or improved photos. Especially relevant when someone gains muscle while losing fat, which can hold the scale flat while the body visibly changes.
Go deeper
These concepts are covered in depth in the weight-tracking guides, and you can apply them directly with the free BMI calculator, calorie deficit calculator and weight loss goal calculator.