Every TDEE calculator does the same thing: estimate your resting burn from height, weight and age, then multiply it by an activity factor you pick from a list. For an athlete that list is useless. “Very active” covers a recovery week and a 15-hour build week alike, and the gap between them is 1,000 kcal a day or more.
AiTrainingPlan uses the formula only as a starting point. It then does two things a calculator cannot: it corrects the number from what your body actually did, and it adds the workouts you are about to do.
Layer 1: the baseline that corrects itself
- Prior. A formula estimate: Katch-McArdle when your body fat is known, Mifflin-St Jeor otherwise, with an uncertainty of about ±250 kcal.
- Observation. Your average logged intake plus the slope of your fasted weight trend times 7,700 kcal per kg. If you ate 2,400 kcal a day and lost 0.25 kg a week, the observed burn is about 2,675 kcal.
- Blend. The two are combined Bayesian-style, each weighted by how certain it is. With little data the formula dominates; after four weeks of consistent logging your own data does.
- Confidence. You get a range, not just a number, plus a data-quality score built from logging consistency, weigh-in frequency and how confident each food entry is.
Weigh-ins flagged as not fasted are excluded. A post-breakfast reading on a gym scale can move the slope, and with it the estimate, by hundreds of kcal a day. If you start a deliberate diet change, the model trusts the observed number less until the new pattern settles.
Layer 2: the workouts you are about to do
The baseline tells you what an average day costs. Training days are not average. AiTrainingPlan adds a training burn on top, averaged over three days: what you actually burned the two days before (from Garmin and intervals.icu) and what today’s planned session should burn. The carbs arrive around the long ride, and one monster session is spread over the days that need to refuel it instead of spiking a single day.
Layer 3: a deficit that backs off when you are tired
If you are cutting, you choose a deficit: 10%, 15%, 20% or 25%. The plan then adjusts it to your training stress balance (TSB). When you are carrying heavy fatigue the deficit shrinks, by up to half when TSB falls below −20, and returns to full once you are fresh. You lose weight in the weeks that can afford it and keep fuelling the ones that cannot.
| Typical TDEE calculator | AiTrainingPlan adaptive TDEE | |
|---|---|---|
| Starting point | Formula × activity level | Formula as a prior only |
| Corrects from your data | No | Yes: intake vs fasted weight trend |
| Training days | Same number every day | Planned workouts added per day |
| Deficit vs fatigue | Fixed | Shrinks with negative TSB |
| Uncertainty | Hidden | Range and data-quality score |
Where it shows up
The same TDEE drives your daily calorie and macro targets, and the energy-balance part of the next-morning weight prediction. If the prediction keeps missing in one direction, that is often the first sign your TDEE is drifting, and you will see it in the log before you see it on the scale. Founder Thomas Prommer publishes the TDEE each of his predictions used on his live log.
Want a quick number first? The free TDEE & macro planner gives you a formula-based weekly plan in a minute. The theory of why formula TDEEs miss for athletes is covered on hybridathlete.guide in TDEE for athletes. See also how the workout log feeds it: a workout log that sets your calories.
FAQ
What is an adaptive TDEE?
A TDEE estimate that is corrected by what actually happened. If you ate an average of 2,400 kcal a day for four weeks and your weight trend fell 0.25 kg a week, you burned about 2,675 kcal a day, whatever a formula said. An adaptive TDEE keeps recalculating that from your own food log and weigh-ins.
How long does an adaptive TDEE take to become accurate?
AiTrainingPlan needs 14 days of logging before it trusts your data and treats 28 days as the full window. Before that it uses a formula and tells you so, with a wider confidence range.
Why is my TDEE different on training days?
Because a two-hour ride can burn as much as a whole rest day’s activity. The adaptive estimate gives your baseline, and a training burn is added on top: the average of what you burned the two days before and what today’s planned session should burn. Hard blocks are fuelled and rest days are not overfed.
Does it use weigh-ins taken after breakfast?
No. Readings flagged as not fasted are left out of the calculation, because a single post-breakfast reading can shift the weight slope, and with it the estimate, by hundreds of kcal a day.