How Much Weight Can You Lose in a Week? Realistic Numbers

0.5 to 1 kg (1 to 2 lb) a week. That is roughly 2 to 4 kg (4 to 9 lb) a month, and 6 to 12 kg (13 to 26 lb) over a quarter. It sounds slow written down and it is not: a year at the lower end of that band is 25 kg.

Two things immediately complicate it.

• The first week is bigger, often 2 to 4 kg (4 to 9 lb). Cutting calories - especially carbohydrate - empties your glycogen stores, and glycogen holds about three grams of water for every gram of itself. Less food and fluid sitting in your gut and a lower sodium load add to it. All of that weight is real on the scale and none of it is fat, so it comes off once and never repeats.
• A fixed number fits nobody. 1 kg a week is a routine rate at 130 kg and an aggressive one at 60 kg. The rate that scales is 0.5% to 1% of your current body weight per week, which is what the first table below works out for you.

Anything faster than that band, sustained, is not a better plan - it is the same plan with more of the loss coming out of muscle. That trade-off is covered further down.

The 0.5-1% band, applied to a range of starting weights. Read your row, and treat the left-hand column as your default and the right-hand one as the ceiling.

Notice that the band moves down as you do. At 100 kg, 1 kg a week is inside the guidance; by the time you reach 75 kg it is not, and the same routine that was producing steady loss will start taking a bigger share from lean tissue. The last few kilograms should be the slowest ones you do - the closer you are to a healthy weight, the less spare fat there is to draw the deficit from.

A kilogram of body fat stores roughly 7,700 calories (about 3,500 per pound). Divide by seven and you get the daily gap between what you eat and what you burn that each weekly rate implies.

Treat this as a rough rule, not a formula. The 7,700 kcal figure is an average for fat tissue, and it systematically overestimates long-run loss for two reasons: some of what you lose early is water and lean tissue rather than fat, and a lighter body costs less to carry and to run. Everyday movement also tends to fall unconsciously when you are in a deficit. Real-world results consistently run slower than the arithmetic after the first month, which is the main mechanism behind most weight loss plateaus. Expect the same deficit to buy you less each month, and adjust rather than assume something has broken.

The bottom row is the useful one for calibration. A 2,200-calorie daily deficit exceeds the entire daily energy needs of a great many adults, which is why 2 kg a week is not something you can simply decide to do.

Faster is not braver, and the costs are documented rather than theoretical:

• More of the loss is muscle. Larger deficits take a bigger share from lean tissue. Muscle is metabolically active, so losing it lowers the level you have to eat below in future - the classic setup for regain.
• Gallstones. Rapid loss is a recognised risk factor, which is why supervised very-low-calorie programmes monitor for it.
• Nutrient shortfalls and fatigue. Below roughly 1,200-1,500 kcal a day it becomes genuinely hard to cover protein, iron, calcium and B vitamins. Tiredness, poor recovery, hair thinning and feeling cold follow.
• Hormonal and menstrual disruption. Prolonged severe restriction can affect cycles and bone health.
• Regain. The most common outcome of a crash diet is not danger but abandonment, and weight regained after aggressive loss tends to come back with a worse ratio of fat to muscle.

Faster rates do have a legitimate clinical place. Medically supervised very-low-calorie diets - typically around 800 kcal a day, for a defined number of weeks - are used for specific reasons, such as preparing for surgery or treating type 2 diabetes, with blood tests, nutritional supplementation and a planned reintroduction of food. What makes that safe is the supervision and the exit plan, neither of which you can improvise from an article. If you think you need to lose weight quickly for a medical reason, that is a conversation with your doctor.

This is the single most common reason people conclude their plan has stopped working when it has not. Weekly numbers are noisy, and the noise is bigger than the signal you are looking for.

• Glycogen and water. Week one drains the tank; week three has nothing left to drain. Refill it with one carbohydrate-heavy weekend and 2 kg reappears - which would be about 15,000 surplus calories if it were fat, so it plainly is not.
• Sodium. A salty meal can hold 1 to 2 kg of water for a day or two.
• The menstrual cycle. Fluid retention in the days before a period routinely masks a week of real loss, then releases it all at once.
• Gut contents, hydration, training. Food in transit, how much you have drunk, and unaccustomed exercise (which causes temporary fluid retention in the muscle) all move the number by a kilogram or more.

The fix is not a better scale, it is a longer window. Compare this week's average against last week's average, never Monday against Monday, and judge the plan on a four-week trend. A useful rule: if your four-week trend sits inside the band in the first table, the plan is working, whatever any single morning said. More on the mechanics in why your weight fluctuates daily and how to break a plateau.

Three steps, and none of them require anything more than a scale you already own:

• Weigh under the same conditions. Morning, after the toilet, before food or drink, minimal clothing. Daily is fine if the number does not bother you; three or four times a week is enough. See how often to weigh yourself.
• Average each week. Add the week's readings and divide. That average is your data point; the individual mornings are not.
• Read the four-week trend. Take the difference between the oldest and newest weekly averages, divide by the number of weeks, and compare it with your row in the first table. Ignore anything shorter than a month, and ignore the first two weeks of any new plan entirely - they are water.

The arithmetic is trivial; keeping four weeks of it in one place is the part people give up on. Weight Journal is a free app that does the recording and the trend line for you - charts over any period so a rate is a slope you can look at, goal tracking, weight alongside BMI and body fat percentage so you can see the quality of the loss as well as the quantity, Apple Health sync, and export to PDF or CSV if you want to show a clinician. It syncs through iCloud with no account and no email address.

Whatever you record it in, the discipline is the same: pick a rate you could still be running in six months, measure it in weekly averages, and judge it monthly.