People treat maintenance calories like a personal constant. It isn't — it's a moving average that responds to at least five inputs, which is why the number that held you steady in January doesn't in June.
The five movers
Body weight — the big one: every kg up or down shifts total burn ~15–25 kcal/day. Activity drift — a new job, season, injury or commute change can move NEAT by hundreds of kcal/day without a single gym decision. Dieting state — in a deficit, adaptation suppresses maintenance 5–15%; at steady feeding it drifts back. Training load — both the sessions themselves and added muscle (each kg of muscle burns ~13 kcal/day at rest — modest, but it compounds with the heavier training it enables). Age — slower than advertised: research shows expenditure is roughly stable from 20 to 60 after adjusting for body composition; the “metabolism died at 35” effect is mostly activity and muscle loss, both negotiable.
What this means practically
Any calculated maintenance number has a shelf life. Recalculate after every ~5 kg of weight change or any lifestyle shift, and prefer measurement to estimation: two to three weeks of intake and scale data in the actual TDEE calculator gives your current maintenance, adaptation and all. If you're holding after a diet, the maintenance phase guide covers the expected drift in the first months, when the number is at its least stable.
Frequently asked questions
How often should I recalculate maintenance calories?
After every ~5 kg of weight change, any meaningful lifestyle change, or every 8–12 weeks during an active phase. Between recalculations, the scale trend is your live feedback.
Why is my maintenance lower than my friend's at the same weight?
Different muscle mass, different NEAT, different training, and normal ±10% individual variation in BMR. Identical stats on a form never meant identical metabolisms.
Does metabolism really slow with age?
Far less than folklore says: major research finds expenditure roughly stable from 20–60 once size and composition are accounted for. Preserving muscle and movement preserves most of the number.
My maintenance seems higher after months of eating at it — possible?
Yes. Recovery from adaptation, restored NEAT and improved training can all lift expenditure at stable weight. It's the mirror image of the suppression that happened while dieting.
More guides
- What Is TDEE?
- What Is BMR?
- Mifflin-St Jeor Calculator
- Harris-Benedict Calculator
- Katch-McArdle Calculator
- BMR vs TDEE: What's the Difference?
- What Are MET Values?
- What Is NEAT?
- The Thermic Effect of Food
- Activity Multipliers Explained
- What Is a Calorie?
- Metabolic Adaptation Explained
- The Calorie Deficit, Explained
- 500-Calorie Deficit
- 1,000-Calorie Deficit
- 300-Calorie Deficit
- How Many Calories to Lose 1 Pound a Week
- How Many Calories to Lose 2 Pounds a Week
- Reverse Dieting
- Maintenance Phase
- Calorie Cycling
- How Accurate Are TDEE Calculators?
- Not Losing Weight in a Calorie Deficit? 7 Real Reasons
- Is 1,200 Calories a Day Safe?
- Should You Eat Back Exercise Calories?
- How Long Does Metabolic Adaptation Last?
- Do You Burn Fewer Calories as You Lose Weight?
- Calorie Cycling vs Flat Deficit
- How to Avoid Muscle Loss on GLP-1 Medications
Sources
- Pontzer H, Yamada Y, Sagayama H, et al. Daily energy expenditure through the human life course. Science. 2021. [link]
- Leibel RL, Rosenbaum M, Hirsch J. Changes in energy expenditure resulting from altered body weight. N Engl J Med. 1995. [link]
- Levine JA. Non-exercise activity thermogenesis (NEAT). Best Pract Res Clin Endocrinol Metab. 2002. [link]