In a calorie deficit and still not losing weight

1. You eat more than you think

This is the most common reason, and it has nothing to do with discipline. In a study in the New England Journal of Medicine, researchers examined ten people who said they could not lose weight despite dieting. Their energy use was normal, within 5 % of the expected value. But on average they had eaten 47 % more than they wrote down. They overestimated their activity by 51 %.

If you estimate instead of weigh, you usually come out low. The usual gaps:

• Oil and butter for cooking. A tablespoon of oil has about 90 kcal and is missing from almost every log.
• Drinks. Juice, milk in your coffee, the beer in the evening.
• Small bites. The piece of cake at work, the rest on the plate.
• Portions by eye. A handful of nuts quickly turns into 50 g instead of 30.

What helps: weigh everything for two weeks, the oil in the pan included. Then you know how well you estimate, and you can relax again.

2. The weekend cancels out the week

A deficit counts over the whole week, not per day. Stay 500 kcal below maintenance from Monday to Friday and you save 2,500 kcal. If Saturday and Sunday each run 1,250 kcal over, the week sits at zero. That is about one pizza and two beers more than usual on each of the two days.

So count with the weekly average. Plan the weekend in instead of making the week stricter and stricter.

3. You measure for too short a time

Fat goes slowly, water swings fast. With a 500 kcal deficit a day you lose about 450 g of fat a week. Water, salt and digestion move the scale by 1 to 2 kg. A week of progress can disappear in that completely.

So watch the 7-day average and only draw conclusions after two to three weeks. Why single days jump is in Why the scale jumps after the weekend.

If you have a cycle

The cycle moves water too. In a study over one year, 62 women noted every day how much water they retained. It was highest on the first day of the period and lowest in the middle of the first half of the cycle. So compare your average with the same phase last month, not with the week before.

4. Your maintenance is lower than calculated

Every calorie calculator estimates from height, weight, age and activity. Your body does not follow the formula. It can sit above or below it.

Fitness watches are even less exact. Researchers at Stanford tested seven wrist-worn devices against a measurement of breathing gases. None estimated energy use with less than 20 % error. Eat back your watch's calories and you count with a number that can easily be a fifth off.

What helps: take the calculated maintenance as a starting point and let your data correct it. If you eat the same, weighed, for three weeks and the average stays put, that is your real maintenance. Leave out the watch's calories.

5. Your energy use drops too

A lighter body needs less. A smaller body uses less energy, lying down as well as walking. The deficit you started with gets smaller with every kilo, even if you eat exactly as on day one. A model in The Lancet shows why: weight responds slowly to eating less, and the curve flattens over time.

On top of that comes an adjustment. In one study, people who had lost 10 % or more afterwards used 6 to 8 kcal less per kilogram of lean mass a day than before. At 60 kg of lean mass that is 360 to 480 kcal. Part of it was in resting energy use, part in movement.

You also often move less in daily life without noticing. In a six-month study, activity dropped after three months in those who only ate less. In those who also followed a fixed training plan, it did not.

What helps: count your steps and keep them steady. Keep training by plan. If the curve flattens after months, that is not a mistake. It is the moment to set your calories again.

6. You are building muscle at the same time

If you start lifting or come back after a break, you often build muscle while fat goes. The scale then shows little, but your body still changes. A review shows that trained people can do this too, with progressive training and the right food, above all enough protein.

How you spot it: your waist gets smaller, your strength goes up, your trousers sit looser. Measure your waist once a week, in the morning, at the height of your navel. The protein calculator shows your protein number.

The order to check in

1. Do you weigh your food, oil and drinks included? If not, start there.
2. What does the average of the whole week look like, weekend included?
3. Do you watch the 7-day average, over at least three weeks?
4. Do you eat back your watch's calories?
5. Is your waist getting smaller, even if the scale stays put?

Only when all of that fits, cut your calories by 100 to 200 a day or walk more. Change one thing at a time and give it two to three weeks.

What to avoid

• Eating even less without checking. If the weekend is the cause, a stricter week only helps until Saturday.
• Starving for a day to make up for the day before. It makes the week harder to keep. Plan the weekly average instead.
• Cutting back on lifting. It tells the body that it needs the muscle. How to keep it in a deficit is in Lose fat without losing muscle.
• Blaming your metabolism. In the study above, energy use was normal. Most of the time it is one of the six causes.