Quick answer: No. One kilogram of fat holds about 7,700 calories, so losing a kilo of fat per day would require burning 7,700 more calories than you eat, daily. Even elite endurance athletes in competition rarely approach that. What people see on the scale in a single day is water, food weight and waste — all of which return.
Why the scale can still drop a kilo overnight
Body weight fluctuates by 1–2 kg within a normal day, and none of it is fat. You lose water through breathing and sweating overnight. A salty dinner holds water; the next day it releases. A large meal sits in the gut and weighs what it weighs until it does not. Glycogen shifts take water with them at about three grams of water per gram of carbohydrate.
All of this is real weight on a scale, and none of it is the thing you are trying to lose.
The danger of chasing a daily number
Weighing daily and reacting to each reading is how people end up cutting food further on a day when they were simply retaining water. That is the start of a restrictive cycle that damages the metabolic rate and, for some people, the relationship with food.
The fix is simple: weigh at the same time under the same conditions, and read the weekly average rather than the daily figure. A genuine downward trend is visible in a fortnight and invisible in a day.
What a real daily rate looks like
Sustainable fat loss runs at roughly 0.5–1% of body weight per week. For an 80 kg person that is 0.4–0.8 kg per week — which is a little over 100 grams a day, on the good weeks. It is undramatic, and it is the rate that actually accumulates into 10 kg by the end of the year rather than 10 kg lost and regained four times.
Where the "1 kg a day" claims come from
Usually the first two days of a very low carbohydrate or very low calorie diet, where glycogen water leaves rapidly. The claim is technically describing something that happened on a scale. It is not describing fat, it does not continue, and it reverses on refeeding.
