Not Losing Weight on a Calorie Deficit? Here Is Why

First, check the deficit is actually there

The first thing people say when the scale won't move is "my metabolism is slow". The second is "my body went into starvation mode". Before reaching for a complicated explanation, check the simple one. Most of the time the deficit exists in your head and in the calculator, but not on your plate.

Where it goes missing:

• Snacks you didn't log. A piece of cheese while you chop the salad, two cookies with tea, a spoonful from the pot "just to taste". Nothing on their own, a real number by the end of the day.
• Oil. You greased the pan, drizzled the salad, and the log says "chicken breast with vegetables", as if they cooked themselves.
• Drinks. Lattes, juice, a glass of wine in the evening. Almost nobody logs them.
• Weekends. Five days on target, then Saturday and Sunday eat what you saved on weekdays. The week nets out at zero.
• Eyeballed portions. Over time "one spoon" quietly becomes a spoon and a half, and "a bowl of rice" becomes two.

There's only one way to check: log everything for a week, right after eating, not from memory at night. Not to beat yourself up, but to see the real number. If an honest week shows there was no deficit, that's good news: nothing is broken, the food just needs adjusting. The spots that eat a deficit most often, and how to set up a week where the weekend doesn't cancel the weekdays, are covered in a plan for your first week in a deficit.

Water weight: why one morning means nothing

The number on the scale isn't just fat. It's also water, what's in your gut, and last night's salty dinner. Those change every day and are usually bigger than the fat that comes off in a week.

So one morning tells you nothing. The scale can go up after a salty pizza, a hard workout or a bad night's sleep, even though you didn't gain any fat overnight. It also works the other way: the number sits still for a week and then drops over a couple of days.

What to do about it:

1. Weigh yourself under the same conditions: morning, after the bathroom, before food and water.
2. Write down every weigh-in, not just the good ones.
3. Once a week, work out your average for the seven days.
4. Compare averages with each other, not one morning with another.

If the weekly average is creeping down, it's working, even when individual days jump around. If the average hasn't moved for two or three weeks with an honest log, that's a plateau, and it's worth digging further.

You lost weight, so your target shrank

This is the reason people forget most often, even though it's the most logical one.

Daily burn is calculated from your weight. The Mifflin-St Jeor equation for resting metabolism, which the calculators on this site use, has weight in kilograms right in it (Mifflin MD, St Jeor ST et al., American Journal of Clinical Nutrition, 1990). Resting metabolism is then multiplied by an activity factor, an approach that comes from FAO/WHO/UNU, Human energy requirements, chapter 5, 2004. Weigh less, burn less. The target that was a deficit at the start is close to maintenance ten kilos later.

Here's what that looks like in numbers. The tables use the same engine as the calculator on this site.

Women:

Woman, 30, 165 cm, light activity (×1.375). The target never drops below 1200 kcal.

Men:

Man, 30, 178 cm, light activity (×1.375). The target never drops below 1500 kcal.

Look at the burn column. The woman in the table burns 2,090 kcal a day at 80 kg and 1,953 at 70 kg. Ten kilos down, and her burn fell by about 140 kcal a day. Say she started at 80 kg eating 1,590 to lose half a kilo a week. At 70 kg the same 1,590 is a deficit of about 360 kcal, not 500. Her pace slowed on its own, and she didn't change a thing.

The fix is simple: every 4-5 kg, recalculate your deficit for your new weight. It takes thirty seconds and answers half of the "why did it stop" questions.

Your activity level is set too high

The activity multiplier is the softest spot in any calculation. People honestly pick "exercise 3-5 times a week", and in practice two of the five sessions happened this month and the rest of the time went by at a desk. The calculator's burn comes out higher than the real one, and the target goes up with it.

Another trap is "eating back" the calories you burned. You walked for an hour, your watch showed a number, and dessert suddenly feels earned. But a walk often burns less than people think, and part of it is already built into the activity multiplier. If you want to know what one walk actually gives you, check the calories burned walking calculator. It's usually less than you'd hope.

If you're unsure which level to pick, go one step lower. Erring that way is safer.

Inches down, scale stuck

It happens: the scale sits still and your jeans get looser. Especially if you've just started lifting or changed your routine a lot.

There can be a few reasons: after new training the body usually holds more water, and beginners may add a little muscle. Which one applies to you, the scale can't tell. That's why the scale shouldn't be your only measure.

Add two more:

• Tape measurements every 2 weeks: waist, hips, chest. Same time of day, same spot.
• Clothes. The same pair of trousers you put on once a week is more honest than any number.

If the measurements are going down while the average weight holds, most likely nothing is broken. Give it another couple of weeks.

What to do, step by step, for 2 weeks

If your average hasn't moved in 2-3 weeks, this is the order I'd go through myself, from simple to less simple:

1. Recalculate your target for your current weight. If you've lost even 4-5 kg, the old number is out of date.
2. Check the activity level. Pick the one that matches a normal week, not your best one.
3. Log everything for two weeks, right after eating. Oil, drinks, snacks, weekends. The easiest way for me is a Telegram bot: a photo of the plate or a voice note saying "latte and a croissant", and the entry is done, no database search.
4. Weigh yourself every morning and work out the average at the end of each week.
5. Take measurements every 2 weeks alongside.

After two weeks you'll have an honest picture. Either it turns out there was no deficit, and you'll see where it was leaking. Or the log is honest, the target is recalculated, and the average still won't move, in which case you can take off another 100-150 kcal.

What not to do: halve your food overnight. The deficit calculator won't set a target below 1,200 kcal for women or 1,500 for men, and you shouldn't go below those on your own either. A harsh deficit is hard to hold and usually ends in a blowout that brings the weight back. If you've been in a deficit for a long time, a couple of weeks at maintenance before going back down is sometimes the better move. More on the deficit itself and on pace: what a calorie deficit is.

When to see a doctor

Sometimes it really isn't about calories. Weight can behave oddly because of medication, hormonal changes or illness. I'm not a doctor and won't try to untangle that, and no article replaces a check-up.

See a doctor if:

• your log is honest, your target is recalculated, and your average weight hasn't changed for a month or more;
• your weight is going up even though you're eating less than usual;
• other changes came along with the weight: constant tiredness, swelling, sleep problems, a changed cycle;
• you take medication and noticed your weight changed after you started it.

Tell the doctor what and how much you eat, and bring your log. Two weeks of honest food records are useful information for that conversation.