How to build a calorie target that is sustainable

The best deficit is the one you can maintain. That sounds like a platitude until you look at what actually separates people who lose weight and keep it off from people who do not, and find that it is almost never the size of the deficit they started with.

Faster is not better

The intuition is that a bigger deficit means faster results, so a bigger deficit is better. Two things undermine it.

Lean mass. In a large deficit a greater share of the weight lost comes from lean tissue rather than fat. That is bad on its own terms and bad for what follows, since lean mass is metabolically active — losing it lowers your maintenance further and makes the next stage harder.

Adherence. Very large deficits are difficult to sustain, and the failure mode is not gradual. People do not drift from a 1,200 kcal target to a 1,400 kcal one; they hold it rigidly for a fortnight and then abandon it entirely. Average intake over three months is what determines the outcome, and a moderate deficit held for twelve weeks beats an aggressive one held for three.

What this site will not produce

The calorie calculator applies limits in code rather than as advice, and it is worth explaining what they are for.

Deficits are capped at the lesser of a quarter of your maintenance level or 1,000 kcal a day. For someone maintaining at 2,000 kcal, that is a 500 kcal cap. Scaling the limit to maintenance matters: a fixed 500 kcal deficit is moderate for a large person and severe for a small one.

There is a floor. No target below 1,500 kcal for men or 1,200 for women. Below those it becomes genuinely difficult to meet micronutrient requirements from food, and intakes in that range are used clinically with supervision and monitoring that a website cannot provide. If your inputs imply something lower, the calculator shows the floor and explains why.

No plan toward an underweight goal. Enter a goal weight below a BMI of 18.5 for your height and the calculator declines to produce a plan, showing the healthy range instead.

No aggressive presets. The fastest option is 0.5 kg a week in either direction. There is no “extreme” or “rapid” setting, partly because the evidence does not support them and partly because those labels encourage a framing this site avoids.

Choosing a rate

Roughly:

0.25 kg a week (about 275 kcal below maintenance). Slow, barely noticeable day to day, and easiest to hold. Good if you are already lean, if you are trying to keep training quality high, or if previous attempts at faster rates have not stuck.

0.5 kg a week (about 550 kcal below maintenance). A reasonable default for most people with a meaningful amount to lose. Fast enough to see progress within a fortnight, slow enough to be liveable.

Anything faster is not offered here, and for people with a lot to lose, a percentage-based rate is a better guide than an absolute one — around 0.5 to 1 per cent of body weight per week is the range most practitioners use, which naturally means larger absolute losses at higher body weights.

What makes a deficit hold

Four things, in rough order of how much they help.

Protein. The most satiating macronutrient per calorie, and the one that best preserves lean mass while energy is short. A target of 1.6 to 2.2 g/kg is well supported, and in a deficit the upper end is justified. See how to set a protein target.

Food volume. Fullness responds to the mass and volume of food more than to its energy. Vegetables, fruit, potatoes, legumes, broth-based soups — all deliver a large amount of food for a modest number of calories. Two meals of identical energy can produce very different hunger.

Fibre. Slows gastric emptying and blunts the appetite response. Most people eat well below recommended intakes, and increasing it is one of the few changes that reliably makes a deficit easier rather than harder.

Consistency over perfection. A week averaging 1,800 kcal with one day at 2,400 beats six days at 1,500 and one at 3,500, even though the totals are similar. The second pattern is also the one that tends to escalate.

Diet breaks and maintenance periods

Extended dieting has costs beyond hunger: reduced NEAT, hormonal changes affecting appetite, accumulating psychological fatigue.

Planned periods at maintenance — a week or two every couple of months — are increasingly common in practice. The evidence on whether they improve fat loss outcomes specifically is mixed, but they clearly help with adherence, and adherence is what determines the result.

What matters more than the protocol: a period at maintenance is not failure. Someone who diets for eight weeks, maintains for two, and diets for eight more will almost always end up further ahead than someone who diets for four weeks and then abandons the attempt.

Set the endpoint before you start

The most common failure is not the diet. It is having no plan for afterwards.

If you lose 10 kg and then return to your original intake, you regain it — that intake was maintenance for the heavier body, and your new maintenance is roughly 150 kcal lower.

Decide before you start what the maintenance phase looks like: what you will eat, how you will monitor, what change in weight triggers an adjustment. A common approach is to increase intake gradually, perhaps 100 kcal a week, until weight stabilises, then hold there deliberately for a while before considering anything else.

The number is a starting point

Whatever the calculator produces, it is an estimate built on an estimate — a BMR equation with roughly ten per cent error, multiplied by an activity factor with a weaker published basis than the equation itself.

Use it for a fortnight. Weigh daily and compare weekly averages, since daily readings are dominated by water and gut contents rather than fat. If the trend matches your intent, the estimate was good. If not, adjust by 100 to 200 kcal and give it another fortnight.

After one round of that you have a number measured on the only person it needs to be right about, which is worth more than anything a calculator can tell you.