How fast is reasonable
Step 3 of 6. "How fast can I lose weight?" usually carries a second, quieter question: why not faster? This page answers both, and the second one is the more useful.
What the guidelines say — and how they have changed
For years the standard advice was a fixed daily deficit of roughly five to seven hundred kilocalories, and intake bands of twelve to fifteen hundred kilocalories a day for women and fifteen to eighteen hundred for men. That comes from an American evidence review of 2013 and it is still quoted everywhere.
The current English guideline deliberately dropped the single number. It asks for an individualised deficit with professional support, and it reserves diets of eight hundred to twelve hundred kilocalories a day for specialist services only — not for self-service tools like this site or the app. Public-health advice in the United States describes a "gradual" pace of about half a kilogram to one kilogram a week; that is population advice for realistic goals, not a medical safety line. The dietetic profession's position paper frames the goal differently again: five to ten percent of starting weight over about six months, with three to five percent already bringing measurable health benefit.
None of these sources defines a weekly maximum. Read together they describe a corridor — slow enough to keep, fast enough to notice — and inside that corridor the pace is a choice.
Why faster costs more than it gains
Two things happen when the deficit is large:
A bigger share of the loss is lean tissue. In a controlled comparison in athletes, the group assigned to lose about 0.7 percent of body weight a week (and achieving roughly that) gained a little lean mass alongside strength training, while the group assigned twice that pace (achieving about one percent a week) held its lean mass unchanged. That is a small study of elite athletes with four strength sessions a week, so it is a physiological signal rather than a rule for everyone; but the direction is consistent with what the systematic reviews of protein intake show: higher protein during a deficit protects muscle, and the protection matters more the faster you go.
Adherence falls. This is the cost nobody prices in. A large deficit is hungrier, more tiring, more socially awkward, and it ends sooner. The pattern that produces the most weight loss in a year is rarely the most aggressive one — it is the one still running in month eight.
Protein and strength work reduce the first cost. Nothing fixes the second except choosing a pace you can keep.
The first weeks are not the rate
The early drop on the scale — often two or three kilograms in the first fortnight — is mostly water and glycogen, not fat. It happens with any reduction in intake and especially with lower carbohydrate. It is real, it is not a lie, and it will not continue. If you set your expectations by week one, week three feels like failure for no reason. The path "Something isn't working" explains the scale in detail.
There is also a quieter mathematical reason the old "a fixed deficit per kilogram" rule disappoints: the energy cost of losing a kilogram depends on how much fat you start with and rises as the loss goes on, because a growing share of what is lost is lean tissue. So the same deficit buys a little less weight each month. That is expected, not a plateau.
How to set your own pace
- Express the pace as a share of your weight, not in kilograms. Half a percent a week means something similar for a 60-kilogram person and a 120-kilogram person; half a kilogram does not.
- Pick a deficit you could hold for months, not ten days. If you are unsure, pick the smaller one — you can always increase it later, and a deficit you abandoned is worth nothing.
- Keep protein and, if you can, two strength sessions a week in the plan (step 4 covers what and why).
- Judge the pace after three weeks of trend, not after the first weigh-in.
The app follows the same logic: you choose the pace as a fraction of your weight, and the plan caps it — as a product rule, not a medical threshold — while its floors stop a lighter body well before the cap. It says on screen when it has reduced what you asked for and why.
What this page does not claim
It does not give a medically safe maximum; no source above does, and this site will not invent one. It does not say a given pace is dangerous or safe for you. And it says nothing more about very-low-calorie diets than the guideline does: specialist supervision only.