How Long Does It Take to Lose Weight?
By Jesse · Last updated August 20, 2026
There is an arithmetic answer to this question, and it is the one every calculator on the internet gives you. It is also consistently too short. This guide gives you the arithmetic answer, then shows how far off it is, then answers the question people are usually asking underneath it: how many weeks until I can actually tell whether this is working?
Everything below is computed from the same simulation behind our analysis of the linear weight-loss model, so the tables and the text cannot disagree. If you want to choose the size of your deficit rather than time one you have already chosen, the calorie target guide is the one to read first.
The arithmetic answer
A kilogram of body fat stores roughly 7,700 kcal, or about 3,500 kcal per pound. Divide the energy you want to shed by the energy you are short each day and you get a number of weeks:
weeks = (kg to lose x 7,700) / (daily deficit x 7)
| Weight to lose | 250 kcal/day | 500 kcal/day | 750 kcal/day | 1,000 kcal/day |
|---|---|---|---|---|
| 2 kg (4 lb) | 9 weeks | 4 weeks | 3 weeks | 2 weeks |
| 5 kg (11 lb) | 22 weeks | 11 weeks | 7 weeks | 6 weeks |
| 10 kg (22 lb) | 44 weeks | 22 weeks | 15 weeks | 11 weeks |
| 15 kg (33 lb) | 66 weeks | 33 weeks | 22 weeks | 17 weeks |
| 20 kg (44 lb) | 88 weeks | 44 weeks | 29 weeks | 22 weeks |
| 25 kg (55 lb) | 110 weeks | 55 weeks | 37 weeks | 28 weeks |
Rounded to the nearest week. 1,000 kcal/day is the largest deficit our planner will set, so the last column is the fastest timeline the site will give you.
This is the model behind our body weight planner and behind almost every other one. It was formalised by Hall and colleagues in a 2011 Lancet paper on energy imbalance, and it is a reasonable first approximation. The problem is what it holds constant.
Why every number in that table is too short
The straight line assumes your deficit stays the size you set it. It cannot. Your deficit is the gap between what you eat and what you burn, and what you burn falls as you get lighter: there is less tissue to maintain and less mass to move. At moderately active (3–5 days/week), maintenance calories drop by about 15.5 kcal a day for every kilogram lost. Hold your food intake still and your deficit closes by itself.
Recomputing maintenance every week from the new body weight gives the honest version of the same table. For a 500 kcal starting deficit:
| Weight to lose | Straight-line planner | Maintenance recomputed weekly | Difference |
|---|---|---|---|
| 2 kg (4 lb) | 4 weeks | 5 weeks | +1 week (+14%) |
| 5 kg (11 lb) | 11 weeks | 12 weeks | +1 week (+9%) |
| 10 kg (22 lb) | 22 weeks | 26 weeks | +4 weeks (+18%) |
| 15 kg (33 lb) | 33 weeks | 44 weeks | +11 weeks (+33%) |
| 20 kg (44 lb) | 44 weeks | 68 weeks | +24 weeks (+55%) |
| 25 kg (55 lb) | 55 weeks | 105 weeks | +50 weeks (+91%) |
The third column holds food intake constant and lets maintenance calories fall with body weight. It models only that one effect, so it is still the optimistic case.
The error is small for small goals and severe for large ones. Two kilograms arrives essentially on schedule. Ten kilograms slips from 22 to 26 weeks. Twenty kilograms slips from 44 to 68 weeks — from under a year to well over one. The practical rule: trust a linear planner for the next two or three months and re-run it, rather than reading a date off it for a goal a year away.
And even the recomputed column is generous. It lets maintenance fall only through body weight. It does not include adaptive thermogenesis — the further reduction in expenditure that sustained restriction produces beyond what the weight change explains — or the drop in spontaneous daily movement that tends to come with it. Both push real timelines longer still.
Every fixed intake has a finish line
Follow the logic to its conclusion. If maintenance falls as you lose weight and your intake never changes, then at some weight your maintenance calories equal your intake and loss stops — not from lack of discipline, but because the deficit has been used up. That weight is fixed by the size of your original deficit:
| Starting daily deficit | Total loss before it stalls | Weeks to reach half of that loss | Weeks to lose 10 kg |
|---|---|---|---|
| 250 kcal/day | 16.1 kg (35 lb) | 49 weeks | 68 weeks |
| 500 kcal/day | 32.3 kg (71 lb) | 49 weeks | 26 weeks |
| 750 kcal/day | 48.4 kg (107 lb) | 49 weeks | 17 weeks |
| 1,000 kcal/day | 64.5 kg (142 lb) | 49 weeks | 12 weeks |
Moderately active (3–5 days/week) throughout. The stall point is where the arithmetic runs out, not a recommended goal weight — for the larger deficits it sits below any sensible target and never binds.
Two things are worth pulling out of that table. First, a small deficit has a small ceiling: at 250 kcal a day the arithmetic runs out after 16.1 kg, so a 20 kg goal is not slow at that intake, it is unreachable without changing something. Second, the middle column is the same in every row — 49 weeks. The time to get halfway to your eventual result does not depend on how aggressive the deficit is; it depends only on how fast maintenance falls per kilogram, which is set by your activity level. A bigger deficit moves the finish line further out, it does not get you there sooner in relative terms.
The fix is not a bigger deficit. It is to re-run the numbers as your weight changes — every 5 kg is a reasonable trigger — so your target tracks your new maintenance instead of drifting up to meet it. Put your current weight into the TDEE calculator and reset the target from there.
Your starting weight barely affects the timeline
This surprises most people. Run the same simulation for a 100 kg man and an 85 kg woman at the same activity level and the same 500 kcal deficit: 10 kg takes 26 weeks for the man and 26 weeks for the woman. Their calorie numbers are nothing alike — he maintains his weight on 2,992 kcal a day and she maintains hers on 2,356 — but the number of weeks is the same.
The reason is in the equation. In Mifflin-St Jeor the weight coefficient is 10 kcal per kilogram for both sexes, so maintenance falls by the activity factor times 10 for every kilogram lost, no matter what the starting weight was. Starting weight sets how much food the plan allows; it does not set the pace. What does change the pace is the deficit you can sustain, and a heavier person can usually hold a larger one in absolute calories without eating uncomfortably little. That, not a faster metabolism, is why heavier people often lose faster.
Activity level nudges it, in the direction you would not expect
At a fixed deficit, a more active person spends more calories per kilogram of body weight, so their maintenance falls faster as they lose — and their deficit erodes faster with it:
| Activity level | Maintenance lost per kg of body weight | Weeks to lose 10 kg | Weeks to lose 20 kg |
|---|---|---|---|
| Sedentary (little or no exercise) | 12 kcal | 25 weeks | 60 weeks |
| Lightly active (1–3 days/week) | 13.8 kcal | 26 weeks | 64 weeks |
| Moderately active (3–5 days/week) | 15.5 kcal | 26 weeks | 68 weeks |
| Very active (6–7 days/week) | 17.3 kcal | 27 weeks | 74 weeks |
| Athlete (twice-daily training) | 19 kcal | 28 weeks | 82 weeks |
Same starting deficit in every row. Being more active does not make a fixed deficit slower to act; it means a fixed intake has less headroom before maintenance catches up with it.
The spread is modest over 10 kg and real over 20: 60 weeks sedentary against 82 weeks for someone training twice a day. This is not an argument against exercising. An active person starts from a much higher maintenance figure, so the same deficit leaves them eating far more food, and training protects lean mass while the weight comes off. It is an argument for re-checking your target more often the more active you are.
How long before you can tell it is working
This is the question behind the question. Body weight moves by a kilogram or more from day to day on food volume, sodium, glycogen, hydration, digestive contents, and hormonal cycles. Weight also follows a weekly rhythm in most people — up over the weekend, down across the week — which one 2014 analysis of daily self-weighing documented directly. Set that against how much fat loss a week actually buys:
| After | Expected loss | Can you see it on the scale? |
|---|---|---|
| 1 week | 0.5 kg (1.1 lb) | Smaller than a single day's swing |
| 2 weeks | 0.9 kg (2.0 lb) | Smaller than a single day's swing |
| 3 weeks | 1.3 kg (2.9 lb) | Visible on a 7-day average, not on one weigh-in |
| 4 weeks | 1.8 kg (4.0 lb) | Visible on a 7-day average, not on one weigh-in |
| 6 weeks | 2.6 kg (5.7 lb) | Clear on a 7-day average |
| 8 weeks | 3.5 kg (7.7 lb) | Clear on a 7-day average |
Compared against a 1 kg day-to-day swing, which is at the low end of normal. Losses are taken from the weekly-recomputed simulation.
A single weigh-in cannot detect a week of good work. Cumulative loss does not clear a 1 kg swing until week 3, and a wider swing pushes that further out. That is not a reason to weigh less often — it is a reason to weigh more often and read the average:
- Weigh at the same point in the day, ideally in the morning after using the bathroom and before eating or drinking.
- Record every day and judge the 7-day rolling average, never a single reading. A full week of data averages the weekly rhythm out.
- Compare this week's average with the average three or four weeks ago, not with yesterday.
- Only conclude nothing is happening after three consecutive weeks of a flat average while you are confident in your intake. Then cut 200 to 300 kcal or add activity — not both, and not more.
The first two weeks lie in the other direction
Early on the scale usually falls faster than any of the tables above predict, and it is not fat. Cutting calories, and especially cutting carbohydrate, draws down the glycogen stored in liver and muscle, and glycogen is stored with roughly three times its own weight in water. A few hundred grams of glycogen therefore takes a kilogram or more of water with it. Kreitzman and colleagues described exactly this in 1992 as the reason early weight loss flatters a diet and early regain alarms people.
Two consequences for a timeline. Do not extrapolate week one: it is the least repeatable week you will have. And do not build the plan around it — if you set a schedule from a first-week loss of 2 kg you will be disappointed by week four for no reason at all. The reverse is also true at the end: a 1 to 2 kg jump after a high-carbohydrate weekend is water returning, not fat gained in two days.
What actually stretches a real timeline
Metabolic adaptation gets the blame, but the largest term is usually simpler: the days you are not in a deficit. A deficit is an average over the week, and a plan followed on weekdays only is a smaller plan than it looks.
| Weekly pattern | Average daily deficit | Weeks to lose 10 kg |
|---|---|---|
| 500 kcal below maintenance every day of the week | 500 kcal/day | 26 weeks |
| 500 kcal below on five weekdays, at maintenance on both weekend days | 357 kcal/day | 40 weeks |
| 500 kcal below on weekdays, 250 kcal above on weekend days | 286 kcal/day | 55 weeks |
| 500 kcal below on weekdays, 500 kcal above on weekend days | 214 kcal/day | 90 weeks |
| 500 kcal below on weekdays, 750 kcal above on weekend days | 143 kcal/day | Never (loss stops at 9.2 kg) |
Each row is run through the same weekly-recomputed simulation, using the pattern's average daily deficit.
Holding 500 kcal on weekdays and simply eating at maintenance on Saturday and Sunday is not a 500 kcal deficit at all — it averages 357 kcal, and 10 kg goes from 26 to 40 weeks. Two days at 500 kcal over maintenance stretches the same 10 kg to 90 weeks. At 750 kcal over on both days the plan never gets there.
Nothing in that table involves metabolism. It is arithmetic, and it is the single most useful thing to know about weight-loss timelines: a smaller deficit you actually hold seven days a week beats a larger one you hold five. If your timeline is running long and your food logging is honest, the weekend is the first place to look.
Putting a date on it
- Get your maintenance calories from the TDEE calculator, then choose a deficit you can hold every day of the week — 500 kcal is a sensible default for most people.
- Read the straight-line answer off the first table, or set a goal weight in the body weight planner for a week-by-week milestone list.
- Add the correction from the second table: roughly a fifth longer for a 10 kg goal, and about half again for 20 kg.
- Plan the first 8 to 12 weeks in detail and treat anything past that as provisional. Re-run both calculators every 5 kg with your new weight.
- Weigh daily, judge the 7-day average, and give any change at least three weeks before deciding it means something.
If you want a model that handles the falling-maintenance problem properly rather than by correction factor, the NIH Body Weight Planner implements Kevin Hall's validated dynamic model. Our planner is the simpler linear one, and is best used as a short-horizon tool you re-run.
Common questions
How long does it take to lose 10 kg?
On the arithmetic every planner uses, a 500 kcal daily deficit loses 10 kg in 22 weeks. Once you allow for maintenance calories falling as body weight falls, the same intake takes about 26 weeks. Allow for the days you are not in a deficit and 40 weeks is a more honest planning figure. Six months to a year for 10 kg is normal, not slow.
How long does it take to lose 20 pounds?
Twenty pounds is about 9 kg, so the answer is close to the 10 kg case: roughly 20 weeks on paper at a 500 kcal daily deficit, and around 23 weeks once the shrinking deficit is accounted for.
Does a heavier person lose weight faster?
In percentage terms, yes; in kilograms at a fixed deficit, no. Maintenance calories fall by the same amount per kilogram lost regardless of where you started, so in this model the time to shed a given number of kilograms depends on the size of your deficit and your activity level, not on your starting weight. A heavier person can usually sustain a larger deficit in absolute calories, which is the real reason heavier people often lose faster.
Why did I lose 2 kg in the first week and almost nothing in the third?
The first week includes glycogen and the water stored with it, which is real weight but not fat. Once that is gone the scale settles down to something closer to the calorie arithmetic. Week three is not a failure; week one was simply not repeatable.
How long should I wait before deciding a plan is not working?
At least three weeks, judged on a 7-day rolling average rather than single weigh-ins. At a 500 kcal deficit the expected loss only exceeds a typical 1 kg day-to-day swing after about 3 weeks, so anything shorter cannot distinguish progress from normal fluctuation.
Can I speed the timeline up?
Only within limits. The site's planner caps the daily deficit at 1,000 kcal, and the commonly cited safe range is 0.5 to 1 kg per week. Larger deficits increase the share of weight lost as lean mass, and they erode faster, so the extra speed is partly borrowed rather than gained. Consistency across the whole week buys more time than a bigger deficit does.
These are estimates from energy-balance models, not medical advice. Individual results vary with body composition, medication, and adherence, and every figure here assumes food intake is measured accurately. If you have a medical condition or a history of disordered eating, work with a doctor or registered dietitian before starting a calorie deficit. See our methodology for the sources behind these figures.