How Long Does It Take to Lose Weight?
By Jesse · Last updated July 16, 2026
The honest answer: it depends on how much you want to lose, how large a calorie deficit you run, and how consistently you hold it. But the math is straightforward and gives you a realistic timeline before you start. This guide walks through how to calculate it and what to expect along the way.
The core math: 7,700 kcal per kilogram
One kilogram of body fat stores approximately 7,700 kilocalories of energy (about 3,500 kcal per pound). To lose that kilogram, you need to create a cumulative calorie deficit of roughly 7,700 kcal. A daily deficit of 550 kcal produces a weekly deficit of about 3,850 kcal — which is close to half a kilogram of fat per week.
This model was quantified in detail by Hall et al. in a 2011 Lancet paper and forms the basis of clinical weight management guidance. It is an estimate — real weight change also involves shifts in water retention and lean mass — but it is the most reliable simple model available.
| Daily deficit | Loss per week | Weeks to lose 10 kg |
|---|---|---|
| 250 kcal | ~0.23 kg | ~44 weeks |
| 500 kcal | ~0.45 kg | ~22 weeks |
| 750 kcal | ~0.68 kg | ~15 weeks |
| 1,000 kcal | ~0.91 kg | ~11 weeks |
Use the body weight planner to calculate a personalised timeline for any goal weight and deficit.
What is a realistic rate of loss?
A commonly cited safe rate is 0.5 to 1 kg (1 to 2 lbs) per week. This corresponds to a daily deficit of roughly 550 to 1,100 kcal. In practice, most people find 500 to 700 kcal/day sustainable — large enough to see consistent progress but small enough to maintain energy, mood, and training performance.
Faster loss is possible, particularly early on when excess water weight also drops. But deficits beyond 1,000 kcal/day increase the proportion of weight lost from muscle rather than fat, and are associated with fatigue, increased hunger, and rebound weight gain. The body also adapts metabolically to large deficits over time, making them progressively less effective.
Why the scale moves faster at first
In the first one to two weeks of a calorie deficit, weight typically drops faster than the math would predict. The main reason is glycogen depletion: when you reduce carbohydrates or overall calories, your body uses stored glycogen (carbohydrate stored in the liver and muscles), and each gram of glycogen holds about three grams of water. Losing glycogen means losing water weight — which is real but temporary.
After this initial phase, the rate slows to something closer to the calorie math. This is normal and does not mean the approach has stopped working. It means the water weight phase is over and actual fat loss is dominating.
Why weight loss slows over time
As you lose weight, three things happen that reduce your calorie deficit:
- Your TDEE decreases. A lighter body burns fewer calories at rest and during movement. Someone who has lost 10 kg is burning perhaps 200-300 fewer calories per day than when they started, simply because they are carrying less mass.
- Metabolic adaptation. Beyond what weight loss alone explains, the body also becomes more metabolically efficient under prolonged calorie restriction — a process sometimes called adaptive thermogenesis. This can reduce expenditure by an additional 100-300 kcal/day in some individuals.
- Less non-exercise movement. People on large deficits often move less unconsciously — fidgeting less, taking fewer incidental steps — which reduces energy expenditure without them realising it.
This is why recalculating your TDEE and calorie target every 5 kg (10 lbs) of weight loss keeps progress steady. Use the TDEE calculator with your current weight to update your target.
How to track progress accurately
Daily weight fluctuates by 1 to 2 kg or more due to water retention, sodium intake, hormonal cycles, and digestive contents. A single weigh-in can look discouraging even when fat loss is happening. The most reliable approach:
- Weigh yourself at the same time each day — morning, after using the bathroom, before eating.
- Track a 7-day rolling average rather than individual readings.
- Judge progress over weeks, not days.
If the 7-day average has not moved for three weeks and you are confident in your intake, it is likely a genuine plateau. The standard response is a small reduction in calories (200-300 kcal/day) or an increase in activity — not a drastic cut.
Putting it together
Start by calculating your TDEE to know your maintenance calories. Then decide on a deficit size — 500 kcal/day is a reasonable default for most people. Divide the total weight you want to lose (in kg) by 0.45 to get the approximate number of weeks at that deficit. The body weight planner automates this and produces a week-by-week milestone table.
Adjust your target every few kilograms as your weight changes, and expect the scale to be noisy week-to-week. The trend over months is what matters.
These are estimates based on energy balance models, not medical advice. Individual results vary based on body composition, metabolism, and adherence. 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.