Why the tracker shows a deficit but weight remains the same

The app has shown a deficit for four weeks, but the scale hasn't moved. This situation looks like a violation of physics, but it is explained by five factors, none of which involve a "broken metabolism." All five are measurable, and the magnitude of each is well-known.

Reason one: more eaten than recorded

This is the most common and the most boring reason. Objective measurements show a systematic underreporting of intake; a review of traditional dietary assessment tools describes their tendency toward inaccuracies and points out that new approaches are necessary for this very reason — Frontiers in Nutrition.

Underreporting is not evenly distributed across food items. Fat is the most frequently missed: it is invisible in a prepared dish and contains 9 kilocalories per gram. Next are drinks, sauces, and food eaten while standing.

This is verified not by self-analysis, but by changing the recording method: logging at the moment of eating instead of reconstructing it in the evening usually increases the daily total by a noticeable amount.

Reason two: expenditure is lower than shown

The "burned" number is not a measurement. It consists of an estimate of basal metabolic rate based on a formula and an activity estimate from sensors. Even the best formulas fall within 10% of measured resting expenditure for only some people — see the figures in our article on the calorie calculator.

The estimation of training expenditure by a fitness tracker adds its own error, usually in the direction of overestimation — see the article on fitness trackers and calorie expenditure. If an app adds "calories burned during exercise" to the daily limit, both errors compound in the same direction.

Reason three: water masks changes in fat mass

A kilogram of fat is about 7,000 kilocalories, and with a deficit of 500 per day, it takes about two weeks to lose it. Over those same two weeks, weight can fluctuate by two or three kilograms for reasons unrelated to fat.

• Glycogen. Each gram of glycogen holds about three grams of water. Changes in carbohydrate intake shift weight within a day.
• Salt. A single salty dinner can cause fluid retention for a day or two.
• Cycle. Fluid retention during the luteal phase is a common occurrence.
• Unaccustomed exercise. Muscle inflammation after a new workout causes water retention.
• Intestinal contents. Depends on fiber volume and regularity.

It makes sense to read such scales using a weekly moving average rather than a single morning measurement. Precise arithmetic of adipose tissue is in the article on how many calories are in a kilogram of fat.

Reason four: expenditure decreases along with weight

Part of the decrease in expenditure is simple: a smaller body burns less. But the decrease can be greater than what is predicted by mass loss, and this excess is called metabolic adaptation.

The most well-known data were obtained from participants in "The Biggest Loser" television show. Six years after the competition, 14 out of 16 participants had a resting expenditure that remained lower than predicted based on body composition and age, despite partial weight regain. Publication in Obesity.

These data were later re-evaluated: a separate study from the same years offers a different interpretation through energy compensation — Obesity. An earlier study linked the magnitude of adaptation to the degree of energy imbalance and changes in leptin — Obesity.

Important: this group is an extreme case, involving extreme rates of weight loss over 30 weeks. It is incorrect to apply the scale of adaptation from this group to a standard deficit. More on plateaus and what is known about them — in the article on weight loss plateaus.

Reason five: measuring the wrong thing

Scales show body mass, but the interest is in fat mass. These values can diverge, especially for those starting strength training: fat is lost, lean mass grows, and the scale stays the same.

It is tempting to check body composition on home bioimpedance scales, but their margin of error in estimating body fat percentage is comparable to the change over several weeks — see the article on smart scales. A more reliable indicator is waist circumference, measured consistently.

How to determine which reason applies to you

This should be analyzed in order of decreasing probability, not at random.

1. Stabilize weight measurement: the same time, the same conditions, a weekly average.
2. Check the completeness of records: log at the moment of eating, including drinks and oil.
3. Stop adding "calories burned during exercise" to the daily limit.
4. Compare the actual dynamics of the two-week average with the expected one and adjust the number itself, not the formula.

How the deficit itself is calculated — in the article on calorie deficit. If there is persistent lack of progress despite careful tracking, it is time to talk to a doctor: expenditure and weight also depend on conditions that are not visible in a food diary.

Count it from a photo

Frequently asked questions

Why does weight not drop despite a calorie deficit?

Five typical reasons: more was eaten than recorded; the expenditure in the app is overestimated; changes in fat mass are masked by water fluctuations; energy expenditure decreased along with body weight; scales show total body mass, not fat mass.

How much do people underestimate their intake?

Objective measurements show a systematic underreporting of intake. Fat is the most commonly missed: it is invisible in a prepared dish and contains 9 kilocalories per gram.

What is metabolic adaptation?

A decrease in energy expenditure greater than what is explained by the reduction in body mass. In participants of reality shows with extreme weight loss, resting energy expenditure remained lower than predicted by body composition and age even six years later.

Why does weight jump by a couple of kilograms in a day?

Because of water. Each gram of glycogen holds about three grams of water; salty food retains fluid for a day or two; the menstrual cycle, unusual physical activity, and bowel contents also play a role. The weekly average matters, not a single morning measurement.

Should I add calories burned during a workout to my daily limit?

Estimating energy expenditure during exercise has its own margin of error and is usually overestimated. If you add it to your limit, the error in expenditure estimation and the underreporting of intake compound in the same direction.

Read next

• Weight loss plateau: why weight stalls and what to do about it — The weight has stayed at the same number for the third week in a row, even though the diet hasn't changed — and the first instinct is usually the same: to cut even more.
• Calorie deficit: how to calculate it and how to hold it — A calorie deficit is the one thing without which weight does not come down.
• Metabolism: is it true that it can be "boosted" and that it can "break" — One person is promised a metabolism boost through spices and frequent small meals, another explains weight plateaus by claiming their metabolism is broken from dieting.
• A week in the food diary: how to read your own numbers — After a week, your diary contains seven numbers, and the first instinct is to compare each one to a target.

This article is for general information. It is not medical advice, a diagnosis, or a prescription for treatment or a diet, and it does not replace a consultation with your doctor. If you have a health condition, are pregnant, take medication, or follow a diet prescribed to you, decisions about food belong with your doctor.

Figures from regulations, guidelines and studies are given as they stood when this article was prepared and may since have changed; check them against the primary sources. This article is not advertising, an offer, or individual advice, and neither the author nor the site owner is responsible for decisions taken on the basis of it.