Why am I not losing weight?

Usually for one of a small number of reasons, and almost all of them are measurable rather than mysterious. Either the scale is not showing fat loss yet, or the calorie deficit is smaller than you think, or the deficit that worked in month one has quietly shrunk. Occasionally there is a medical reason.

What it is almost never is a broken metabolism. That matters, because the fix depends entirely on which of these is actually happening, and each one has a different answer.

It is also worth knowing at the outset that stalling is the norm rather than the exception. A 2024 review reports that weight loss eventually slows, stagnates or reverses in around 85% of cases^{[Journal of Health, Population and Nutrition]}. You are not an unusual failure; you are in the overwhelming majority.

First: the scale is not measuring what you think

Body weight moves for reasons that have nothing to do with body fat. Water, glycogen, salt, food still in transit, hormonal cycles and a hard training session can each shift the number by a kilogram or more in either direction over a single day.

Healthy weight loss runs at roughly 0.5 to 1 kg a week^[NHS]. Daily fluctuation is frequently larger than that. So one reading tells you almost nothing, and three disappointing mornings in a row tell you not much more.

If losing weight looks stalled on a two-week view but your clothes fit differently, believe the clothes. A tape measure round the waist is often a better guide to progress than body weight, particularly early on and particularly if you have recently started training.

How many calories should you actually be eating?

As a general reference the NHS puts average daily needs at around 2,000 kcal for women and 2,500 kcal for men, and suggests reducing intake by about 600 kcal a day for steady weight loss^{[NHS Better Health]}. Those are population averages rather than your numbers, but they are a useful sanity check: if your plan involves eating far below them, something has probably gone wrong in the arithmetic rather than in your willpower.

Are you actually in a calorie deficit?

This is the most common answer by a distance, and it is uncomfortable, because most people are certain they are. Two things go wrong more often than everything else combined, and neither is a failure of willpower.

Your maintenance figure is lower than you assumed. Almost everyone picks their activity level one step too high. "Moderately active" generally means deliberate exercise three to five days a week, not a busy job and a dog. Choosing one level up can add 250 to 400 kcal to estimated maintenance, and if you then subtract 500 from an inflated figure, the real deficit might be 150.

It is worth knowing what those numbers are rather than guessing. The BMR calculator gives the energy your body uses at rest, the TDEE calculator multiplies it for how you actually live, and the maintenance calorie calculator gives the figure that holds your weight steady. Total daily energy expenditure is the number to subtract from; resting energy expenditure alone is not.

More went in than you recorded. Oil in the pan, milk in four coffees, the handful from the packet, the part of the portion nobody weighed, the weekend that was not logged. None of this is dishonesty. Under-recording food intake is one of the best-replicated findings in nutrition research and it applies to everybody, including dietitians.

Keep a food diary for one week and weigh things. Not forever, and not as a lifestyle. As a measurement, the way you would check a suspect reading on any instrument before deciding the instrument is broken. Most people find the gap inside seven days.

Calorie intake creeps for ordinary reasons too. Portion sizes drift upwards without anyone deciding they should. Healthy foods are not automatically low in calories: olive oil, nuts, avocado and granola are all excellent food and all calorie dense. Sugary drinks and fruit juices count fully while doing little to reduce appetite, and in one controlled trial an ultra-processed diet raised energy intake by around 500 kcal a day against an unprocessed one matched for nutrients^{[Journal of Health, Population and Nutrition]}.

Your deficit shrank while you were using it

This is the one nobody warns you about, and it is pure arithmetic. A lighter body needs less energy. Every kilogram lost takes roughly 10 kcal a day off your basal metabolic rate, and more off the total once you account for carrying that smaller body around. So the intake that opened a 600 kcal gap at your starting weight opens a much narrower one twenty kilograms later.

Hold the same intake long enough and the gap closes to nothing. That is a plateau, and it arrives on schedule whether or not anything else changed. The weight loss plateau calculator shows how much of your original deficit is left at your current weight. If it comes out at 150 kcal, that is your answer, and the fix is to recalculate rather than to try harder.

Metabolic adaptation sits on top of this. Resting metabolic rate can drop within days of starting a diet, by more than the loss of body mass alone explains^{[Journal of Health, Population and Nutrition]}. It is real, and it is smaller than most people assume. It does not make further loss impossible, and no amount of it turns a genuine deficit into weight gain.

How long does a plateau normally last?

Two to three weeks without movement is common and not a cause for alarm. Beyond four to six weeks of consistent effort with no movement on a properly measured trend, something has changed and is worth finding: usually the shrinking deficit above, sometimes intake drift, occasionally something medical. That threshold stops you abandoning a working plan in week two, and stops you persisting with a broken one for six months.

Muscle, body composition and the scale

If you have started resistance training recently, body composition can change while body weight barely moves. Gaining muscle while losing fat is most likely in people new to training, returning after a break, or carrying a lot of fat to begin with. Muscle is denser than fat, so losing fat and building muscle at similar rates leaves you visibly smaller at the same weight.

Protein matters here more than almost anything else: it is the part of the diet most associated with holding onto lean tissue in a deficit, and the most filling. The protein calculator gives a range for your weight and says what share of your daily calories it would take up.

What exercise does and does not do

Exercise raises the figure you subtract from. It does not add a second subtraction on top of it, and treating a workout as licence to eat more is one of the more reliable ways to erase a deficit. It also moves the number less than most people expect: an hour of brisk walking is perhaps 250 kcal for many adults, and calories burned in a class are routinely overestimated, by the machine and by us.

Everyday movement counts more than it gets credit for, and an exercise routine you will still be doing in six months beats the one that looked most impressive in January.

Alcohol, sleep and stress

Alcohol is the most commonly missed source of calories in an otherwise careful week. It carries roughly 7 kcal per gram, close to fat, and almost none of it registers as food. Nobody needs to stop drinking to lose weight, but if you eat well all week and nothing moves, the weekend is the first place to look.

Short sleep and sustained stress both make eating harder to control, and sleep changes what you lose rather than only how much. In one trial, participants sleeping 8.5 hours lost 1.4 kg of fat against 0.6 kg for those restricted to 5.5 hours on the same diet^{[Journal of Health, Population and Nutrition]}. Short sleep did not stop weight loss; it shifted more of the loss away from fat.

When it is medical

A small number of people have a genuine medical reason. An underactive thyroid, polycystic ovary syndrome and Cushing's syndrome can all make weight harder to shift, and the NHS lists "weight gain or difficulty losing weight" among the main symptoms of PCOS^[NHS]. Thyroid function has a measurable effect on energy expenditure: one study found a 17% difference in resting energy expenditure across a serum TSH range of 0.1 to 10 mU/L in people taking levothyroxine^{[Journal of Health, Population and Nutrition]}.

Several common medications, including some antidepressants, steroids, beta blockers and insulin, can cause weight gain directly or make losing weight slower. These are worth taking seriously and worth putting in proportion: they are far less common than a mis-set activity multiplier.

What to do next, in order

• Weigh consistently for two weeks and look at the trend, not the days. Take a waist measurement at the same time.
• Recalculate maintenance honestly, choosing the activity level one step lower than feels right.
• Weigh your food for one week. Not forever. As a measurement.
• Check what is left of your deficit at your current weight, and reset the target if it has closed.
• Look at alcohol and liquid calories across a full week, weekends included.
• Give it four weeks before concluding anything.
• See a GP if the picture still does not add up, or sooner with other symptoms.

Most people find their answer in the first three steps. It is rarely one dramatic thing and often two small ones at once.

The part worth keeping in mind

Weight loss is not linear and never was. Every attempt has flat stretches; the graph that runs smoothly down and to the right does not exist outside marketing. A gentler pace you can hold for a year beats an aggressive one abandoned in March, and losing 5% of body weight arrives far sooner than most people's final goal — the weight loss percentage calculator shows where that mark falls for you.

If you want to see what a realistic timeframe looks like from where you are, the weight loss calculator estimates it as a range from your own figures, and the calorie deficit calculator gives the daily target behind whichever pace you choose. Every formula and assumption is set out on the methodology page.