Why Your Maintenance Calories Change Month to Month

Your maintenance calories are not a fixed number. They move with four things: how much you walk, how much you train, how well you sleep, and how much you weigh. A change in any one of them can shift maintenance by 200 to 500 calories a day, which is why a target that worked in June can put on fat in November with the same food.

Below is how much each lever moves the number, with the studies that measured it, and a simple rule for when to update your target.

Where the number comes from

Total daily energy expenditure has four parts. Your resting metabolism, which is what your body burns keeping you alive and is the largest piece. The energy cost of digesting food, roughly 10 percent of what you eat. Your training. And everything else you do with your body that is not training: walking, standing, fidgeting, carrying shopping.

That last part is the one people ignore, and it is the one that changes most. Resting metabolism moves slowly, with bodyweight. Training is a few hours a week. The rest of your movement is every waking hour, and it swings with the season, your job and your mood.

Steps: the biggest lever most people never look at

Levine and colleagues (1999) overfed 16 people by 1,000 calories a day for eight weeks and measured where the energy went. Two-thirds of the rise in daily energy expenditure came from non-exercise activity: fidgeting, standing, moving about. Changes in that activity explained a ten-fold difference in how much fat people gained, with a correlation of 0.77. Some people burned most of the extra food off by moving more without knowing it. Others stored it.

The same lever works in reverse when you diet or when life gets busy. My working figure, which is an estimate and not a measurement, is 35 to 45 calories per 1,000 steps for an 80 kg person. So:

A move from 11,000 steps in a summer of walking to work to 5,000 in a winter of driving is 200 to 250 calories a day. That is the size of most people's entire deficit, gone, with nothing else changed.

Training volume: more than the number of sessions

Two lifting weeks can both be four sessions and cost very different amounts of energy. Sixteen working sets in 45 minutes and twenty-eight sets in 80 minutes are not the same week. An hour of hard lifting is usually 250 to 400 calories. Add a new block with more sets and longer sessions and you can add 100 to 150 calories a day to maintenance across the week without touching your steps.

The reverse matters more. A deload week, a holiday, or an injury that takes out legs for a month drops the training cost. If the food stays the same, the scale answers in three weeks.

Sleep: it changes what the calories do

Sleep does not change maintenance much on paper. It changes what happens to the deficit in practice.

Nedeltcheva and colleagues (2010) put ten overweight adults through the same 14-day calorie restriction twice, once with 8.5 hours in bed and once with 5.5. Same food, same deficit. On short sleep, the proportion of weight lost as fat fell by 55 percent, from 1.4 kg to 0.6 kg. Loss of fat-free mass rose by 60 percent, from 1.5 kg to 2.4 kg. Hunger went up too.

Short sleep also lowers spontaneous movement and training quality, which then pulls maintenance down the next day. So a bad month of sleep shows up twice: fewer calories burned, and more of the weight you lose coming from muscle. For a lifter, that second part is the expensive one.

Bodyweight itself

A lighter body burns less. Leibel and colleagues (1995) measured people after they lost 10 percent or more of their bodyweight: total daily energy expenditure fell by 6 to 8 calories per kilogram of fat-free mass per day. For a lifter with 70 kg of fat-free mass, that is 420 to 560 calories a day less than before the diet. Gaining 10 percent did the opposite, raising expenditure by 8 to 9 calories per kilogram.

Hall and colleagues (2011) added the time dimension. The body's weight response to a change in intake is slow, with a half-life of around a year, and the new steady state is reached gradually, not at once. In practice, a change in food today keeps showing up on the scale for months, which is why "I've been eating the same for ages and I'm still gaining" is usually true and still not mysterious.

A worked example

Chris tested his maintenance in July at 2,900 calories. He was 84 kg, walked to work, averaged 11,000 steps, trained four days with a heavy leg day, and slept seven and a half hours.

In November he is still 84 kg on paper, eating 2,900, and the weekly average has been creeping up: 84.4, 84.8, 85.1, 85.5. He has gained 1.5 kg in six weeks on a "maintenance" diet.

What changed:

• Steps: he started driving in October. 11,000 to 5,000 a day, about 240 calories.
• Training: same four days, but his leg day was replaced by a shorter session after a knee niggle. Call it 50 calories a day across the week.
• Sleep: down to six hours with a new baby. Hunger is up and two of his weekly averages had a takeaway in them.

His real maintenance is now around 2,600. The 2,900 that was true in July is a 300 calorie surplus in November. Nothing broke. The inputs moved.

The fix is not a diet. It is 25 minutes of walking a day to get 3,000 steps back, an honest log for two weeks, and a target of 2,700 while the sleep situation is what it is.

The changes people miss

Most shifts in maintenance are not decisions. They are circumstances, and the common ones are worth naming so you recognise yours.

• Seasons. Summer means walking, evenings outside, weekends on your feet. Winter means the car and the sofa. For many people this alone is 150 to 250 calories a day between July and January.
• Working from home. No commute, no walk to lunch, no stairs. Two to four thousand steps gone, quietly.
• A new baby, a new dog, a new job. The first cuts sleep, the second adds steps, the third can go either way. All three change the number within a fortnight.
• An injury. A month off leg training removes the most expensive sessions of the week and usually the walking that came with them.
• A phone upgrade. Not a real change, but a new step counter can read 20 percent differently from the old one. Compare trends, not absolute numbers, across a change of device.

When to update the number

Update maintenance when one of these is true:

1. Bodyweight has moved 3 to 5 percent from when you last tested it.
2. Your average daily steps have changed by 3,000 or more and stayed there for two weeks.
3. Your training volume has changed for a whole block, not a single week.
4. Three weeks of flat or drifting weekly averages with a clean log.

Do not update it because of one heavy weigh-in, one week of holiday, or one bad night's sleep. The scale reacts to water in a day and to fat in three weeks. Wait for the three weeks. When to recalculate your calories goes through the triggers in more detail.

Common mistakes

Trusting last season's number. A maintenance found in a walking summer is wrong in a driving winter by 200 calories or more.

Counting sessions instead of sets. Four short sessions and four long ones are different weeks. Look at the volume.

Ignoring sleep because it is not food. Short sleep raised hunger and shifted the loss toward muscle in the study above. It is part of the equation.

Recalculating weekly. That reacts to water and undoes good decisions. Three weeks of data or a real change in routine, and only then.

Blaming metabolism first. Steps, sleep and bodyweight explain most of a shifted maintenance. Adaptation is the smallest piece, and why your calorie deficit stopped working has the numbers on it.

How to track this in Ultra+

The reason maintenance shifts go unnoticed is that the inputs live in four different places: a step counter, a training log, a sleep app and a food diary. Ultra+ puts three of them together. The nutrition journal logs your food with search and barcode scan, tracks macros against your target, and logs your bodyweight and sleep, so the weekly average and the nights you actually slept sit next to what you ate.

For training volume, every session shows total volume and the change against your last run of the same workout, so a lighter block is visible as a number rather than a feeling. Previous set and best set are on every set you log, and the weekly card reviews the week you actually did. Steps are the one thing to bring from your phone.

Next

If you have never tested maintenance properly, start with how to find your real maintenance calories. Then, when the inputs move, run the calorie calculator with the new bodyweight and an honest activity level, and hold the new number for three weeks before you judge it.