The base math
A kilogram of body fat stores roughly 7,700 kcal. Hold a 500-kcal daily deficit and you lose about 0.45 kg a week — call it 22 weeks, or five months, for 10 kg. A gentler 400-kcal deficit lands around six months; an aggressive-but-livable 600 kcal shaves it toward four. That's the whole spread: 4–6 months, with your starting size, consistency and honesty setting where you land in it.
The week-by-week shape (so nothing surprises you)
Weeks 1–2: the flattering start
Expect 1.5–2.5 kg down — most of it water and glycogen, not fat. Enjoy it, screenshot it, and do not extrapolate it. This pace was never going to continue and its ending is not a failure.
Weeks 3–8: the real pace emerges
0.4–0.6 kg a week, wobbling around water noise. This is what fat loss actually looks like. The daily zigzag will try to gaslight you — judge only the 4-week trend line.
Weeks 7–10: the danger zone
Novelty gone, compliments not started yet, a flat fortnight likely (salty week, hormones, new workout — pick one). This is where most attempts die. The people who reach 10 kg aren't the ones who avoided this stretch; they're the ones who logged through it.
Months 3–5: the update phase
You're 5+ kg lighter, which means your maintenance calories dropped ~100–150/day. Recalculate (or let your app do it), expect the odd plateau, keep the streak. The last 3 kg move slower than the first 3 — everyone's do.
Reframe that helps: six months sounds long until you notice it's two summers from now either way. In one version you're 10 kg lighter with a year of easy habits; in the other you're googling this again. The time passes regardless.
What makes people actually finish
Not willpower — systems that survive boredom. Logging fast enough to do on bad days (five-second photo beats three-minute database search). A target that updates itself so the math never goes stale. A trend chart that shows progress when the morning number sulks. And a reason to open the app that isn't guilt — which is where a certain hedgehog earns his keep. Streaks turn the boring middle into a game, and the game is winnable: one logged day at a time, twenty-two-ish weeks in a row.