Many people who change how they eat see the scale move quickly at first, then slow, then seem to stop. That is not a sign that something is broken or that you need to eat even less. It is how the body works. Your body spends energy to keep itself going, and the more it weighs, the more energy that takes. When your weight changes, the energy your body needs changes with it.
Think of a see-saw. On one side is what you eat each day. On the other is your maintenance level: the calories your body spends in a typical day (heart, brain, digestion, movement). The distance between the two sides is the gap. While there is a gap, weight keeps moving. As weight moves, maintenance moves towards what you eat, the gap closes, and weight settles at a new steady level. That settling is what people call a plateau.
Each week it works out your maintenance from your current weight, subtracts what you eat, and turns the gap into a small weight change using the rough figure of 7,700 kcal per kilogram of body weight. Then it repeats with your new weight. We show only the gap, not a predicted weight, because no calculator can say how your own body will respond. Maintenance comes from the Mifflin-St Jeor equation (10 × weight in kg + 6.25 × height in cm − 5 × age, then +5 for men or −161 for women) multiplied by an activity factor of 1.2, 1.375, 1.55 or 1.725. These are the same rules of thumb as in our calorie guide.
Even this version is a simplification. The older "3,500 calories per pound" rule assumes the gap stays fixed, and researchers who compared it with carefully supervised studies found it badly overestimates real change. Our model lets the gap shrink, which is closer to life, but real bodies add more: weight also moves with water and muscle, and some people find hunger and daily movement shift when they eat differently.
A plateau usually means your body has caught up with your new weight, not that you have failed.
Notice that a small, steady change already moves things a long way, and that the gap closes by itself. Chasing a bigger gap by eating less is where problems start: very low intakes are hard to keep up, leave you tired and short of nutrients, and public guidance does not recommend going below about 1,200 kcal a day for women or 1,500 for men without professional support. The tool above will not go lower either.
If weight is not your goal at all, the same idea still helps. It shows why a number on the scale from last month does not predict this month, and why judging a way of eating by energy, sleep, hunger and how you feel works better than judging it by one figure. Look at trends over weeks, not days, because water alone can move the scale by a kilo or two overnight.
This guide is general information, not medical advice. If you have a medical condition, are pregnant or breastfeeding, take medication (especially for diabetes or blood pressure), or have or have had an eating disorder, talk to a doctor or registered dietitian before changing how you eat. If your weight changes without you trying, or a stall worries you, ask a doctor too.