How fast should you lose weight? Safe, realistic rates by body weight

The percentage version scales to your body. Here is the deficit each rate needs and why the fast lane usually ends early.

By the Cal.AI Team · Published October 24, 2026 · 4 min read

Short answer A commonly cited safe rate of weight loss is 0.5 to 1 kg (1 to 2 lb) a week, or 0.5 to 1% of body weight per week. Lighter people should sit at the low end, heavier people can use the high end. Faster usually means more hunger, more muscle loss and a plan you abandon.

How fast should you lose weight?

About 0.5 to 1% of your body weight per week. For most adults that comes out at 0.5 to 1 kg (1 to 2 lb) a week, which is the range that is commonly cited as safe and sustainable. The percentage version scales better: 1 kg a week is modest for someone at 130 kg and aggressive for someone at 55 kg.

The reason for a ceiling is not that faster loss is impossible. It is that faster loss needs a bigger deficit, and bigger deficits bring more hunger, more lean tissue loss, a larger drop in energy expenditure and a lower chance that you are still doing it in week ten. Slow and finished beats fast and abandoned.

What 0.5 to 1% per week looks like at different weights

Body weight	0.5% per week	1% per week	Daily deficit needed (rule of thumb)
60 kg (132 lb)	0.3 kg (0.7 lb)	0.6 kg (1.3 lb)	330 to 660 kcal
80 kg (176 lb)	0.4 kg (0.9 lb)	0.8 kg (1.8 lb)	440 to 880 kcal
100 kg (220 lb)	0.5 kg (1.1 lb)	1.0 kg (2.2 lb)	550 to 1,100 kcal
120 kg (265 lb)	0.6 kg (1.3 lb)	1.2 kg (2.6 lb)	660 to 1,320 kcal

The deficit column uses the rule of thumb of about 7,700 kcal per kg (3,500 per lb) of body fat, divided over seven days. It is accurate for the first weeks and then drifts, because a lighter body burns less; see Hall et al. (2011) for why. The top of the 1% column is a large deficit for anyone under about 90 kg, which is why most people should plan around the lower half of the range.

Worked example: a 90 kg woman choosing a rate

A 90 kg (198 lb) woman, 165 cm (5 ft 5 in), 35 years old, moderately active.

Resting metabolism (Mifflin-St Jeor): 10 × 90 + 6.25 × 165 − 5 × 35 − 161 = 1,595 kcal.
Maintenance: 1,595 × 1.55 = 2,472 kcal.
Option A, 0.5 kg a week: deficit 7,700 × 0.5 ÷ 7 = 550 kcal. Target: 2,472 − 550 = 1,922, call it 1,900 kcal.
Option B, 1% a week (0.9 kg): deficit 7,700 × 0.9 ÷ 7 = 990 kcal. Target: 2,472 − 990 = 1,482 kcal.

Option B is nearly 1,000 kcal below maintenance. It is possible on paper and hard in a kitchen: it leaves little room for protein, fiber and any social meal, and it tends to produce the exact weekend overeating that erases the weekday deficit. Option A at 1,900 kcal is a plan she can run for months. A sensible compromise is to start around 1,800, aim for 0.6 to 0.7 kg a week, and recalculate every month.

Why faster usually fails

Hunger and adherence. The larger the deficit, the louder the appetite, and the plan ends not by decision but by drift. Long-term maintainers, as described by Wing and Phelan (2005), tend to share steady habits such as regular self-weighing, consistent eating patterns and high activity, not extreme short-term cuts.

Muscle loss. When the deficit is large and protein is low, a bigger share of the weight lost is lean tissue. Keeping protein around 1.2 to 1.6 g per kg and lifting weights shifts the loss toward fat at any rate, and matters more as the rate goes up.

Adaptation. Energy expenditure drops after weight loss by more than body size predicts (Leibel et al., 1995), and aggressive dieting appears to push that further. A moderate rate keeps the adaptation smaller and the post-diet maintenance easier.

In lean, athletic people the recommended rate is even more conservative: about 0.5 to 1% of body weight per week to limit muscle loss, per the contest-preparation review by Helms et al. (2014). The leaner you are, the slower you should go.

How to set your rate in a calorie app

Most apps, including Cal.AI, ask for your goal, a pace, your activity level, height, weight, age and sex, then build a calorie target with the Mifflin-St Jeor equation. The pace is the setting that matters. Choosing the fastest option feels productive and usually produces the lowest, least livable target.

Pick a pace near 0.5% of body weight a week if you have under 10 kg (22 lb) to lose, or you are already lean.
Pick 0.5 to 1% if you have more to lose, and move to the lower end as you get lighter.
Watch the projected goal date as a sanity check. If it looks impossibly close, the pace is too aggressive.
Re-enter your weight weekly; targets and the goal date update from your current weight.
If the app gives you a very low target, such as well under your resting metabolism, slow the pace. Very low calorie plans belong under a doctor or registered dietitian.

Common mistakes

Judging the rate from the first two weeks, which include water loss and look faster than the real trend.
Using 2 lb a week as a universal target instead of a percentage of your own weight.
Cutting harder when the rate slows, instead of recalculating maintenance at the new weight.
Skipping protein and lifting, so a chunk of the loss is muscle.
Not planning the end. Decide in advance what maintenance looks like, so the deficit has a finish line.

Set a pace you can keep in Cal.AI Cal.AI is free on iPhone, Apple Watch and Android. Snap a photo, scan a barcode or search any food, then fix anything the AI gets wrong.

Frequently asked questions

Is losing 1 kg a week safe?

For someone around 100 kg or more, 1 kg a week is the top of the commonly cited 0.5 to 1% range and is usually workable. For someone at 60 kg it is close to 2% a week and needs a deficit most people cannot hold. Use the percentage of your own body weight, not a fixed number.

Why did I lose 3 kg in the first week?

Mostly water. Cutting carbohydrate and calories empties some glycogen, and each gram of glycogen is stored with about 3 g of water, so the first week shows a drop that is not fat. Lower sodium intake adds to it. Judge your real rate from weekly averages starting in week two or three.

What is the slowest rate worth bothering with?

Any steady rate adds up. A quarter of a kilogram a week is 13 kg (29 lb) in a year, and the deficit behind it, about 275 kcal a day by the usual rule of thumb, is small enough that most people barely notice it. Slow rates fail only when the deficit is so small that logging error swallows it.

Should I lose weight faster if I have a lot to lose?

The percentage handles that for you. At 120 kg, 1% a week is 1.2 kg, which is already a faster absolute rate than a lighter person should attempt. Very low calorie plans beyond that range are a medical decision; talk to a doctor or registered dietitian rather than setting them in an app.

Sources

Helms ER, Aragon AA, Fitschen PJ. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. J Int Soc Sports Nutr. 2014;11:20. PubMed
Hall KD, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826-837. PubMed
Leibel RL, Rosenbaum M, Hirsch J. Changes in energy expenditure resulting from altered body weight. N Engl J Med. 1995;332(10):621-628. PubMed
Wing RR, Phelan S. Long-term weight loss maintenance. Am J Clin Nutr. 2005;82(1 Suppl):222S-225S. PubMed

Cal.AI TeamWe build Cal.AI, an AI calorie counter for iPhone, Apple Watch and Android. Every number in this article links to its source; see how we research and fact-check. This is general nutrition-tracking guidance, not medical advice.