The arithmetic of a kilogram

Body fat stores energy densely, about 7700 kilocalories per kilogram once water shifts are set aside. That single number powers every honest weight loss timeline. Losing half a kilogram a week means running a deficit near 550 kilocalories every day, through eating less, moving more, or the practical mix of both. Double the pace and the deficit doubles with it, which is why aggressive targets fail so often. The daily cost becomes miserable long before the math does.

Why slower usually wins

Large deficits trigger adaptive responses that fight back. Hunger hormones climb, spontaneous movement quietly shrinks, and the body defends its stores. Studies comparing gentle and aggressive approaches repeatedly find that moderate deficits preserve muscle better, feel more livable, and produce similar results a year later because people actually sustain them. A quarter to half kilogram weekly is the band most guidelines endorse for good reason.

Why the scale lies weekly

Glycogen binds water, salt intake shifts fluid, and digestion carries weight of its own. Daily scale readings bounce a kilogram or more around the true fat trend. Judge progress by the weekly average or the trend line across a month, never by a single morning. The calculator gives the fat loss timeline; the scale will dance around it the whole way down.

Pairing with your real numbers

Combine the deficit shown here with your TDEE from the calculator on this site to get an actual daily calorie target. As weight drops, TDEE falls too, so recalculate every five kilograms and adjust the plan. The timeline stretches slightly in reality, and plans that expect the stretch are the ones that finish.

References

• NIDDK. Weight management guidance
• Hall KD and Guo J. Obesity energetics body weight regulation and the effects of diet composition. Gastroenterology 2017